Decades ago I used (on AIX) the 'mailx' command to automatically send
notifications from cron'd shell scripts per email, something like

mailx -s "Test results" me@my.domain.invalid <<EOT
message to deliver
...
EOT

Now on Linux/Ubuntu I get that error

WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
No such file or directory
send-mail: Authorization failed (535 Incorrect authentication data)
Can't send mail: sendmail process failed with error code 1

Two questions:
* Where do I have to look (or what to do)[*] to fix that problem?
* Is there some other (preferred, simpler, or without crypto demands)
interface or tool to send emails automatically from a shell script?

Thanks for any insights.

(References to more appropriate newsgroups are also welcome.)

Janis

[*] I've heard that sendmail configuration is a nightmare.

Janis Papanagnou <janis_papanagnou@hotmail.com> writes:

> Decades ago I used (on AIX) the 'mailx' command to automatically send
> notifications from cron'd shell scripts per email, something like
>
> mailx -s "Test results" me@my.domain.invalid <<EOT
> message to deliver
> ...
> EOT
>
> Now on Linux/Ubuntu I get that error
>
> WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
> No such file or directory
> send-mail: Authorization failed (535 Incorrect authentication data)
> Can't send mail: sendmail process failed with error code 1
>
> Two questions:
> * Where do I have to look (or what to do)[*] to fix that problem?
> * Is there some other (preferred, simpler, or without crypto demands)
> interface or tool to send emails automatically from a shell script?
>
> Thanks for any insights.

It's not email, but notify-send works if you want the message routed to
the desktop.

--
Dan Espen

On Wed, 26 Jan 2022 15:20:04 +0100, Janis Papanagnou wrote:

[snip]
> [*] I've heard that sendmail configuration is a nightmare.

Sendmail configuration is indeed complex, mostly due to the
archaic form of it's configuration file, and the variety of options
available for mail handling.

However, depending on your distro, your installation may have come
with one or more sample configurations, most of which are relatively
easy to modify for use.

I personally run sendmail as my public MTA, with some custom config
changes to handle miltering (raw email filtering) and secured outbound
email relaying (through my ISP's MTA). My sendmail.mc file runs 22 lines
(excluding comments), and only differs from my distro's stock sendmail.mc
by 4 lines.

FWIW, I can recommend
"sendmail"
by Bryan Costales with Eric Allman
O'Reilly & Associates
ISBN 1-56592-222-0
as a /really/ good book on the subject, and
"sendmail Cookbook"
by Craig Hunt
O'Reilly & Associates
ISBN 0-596-00471-0
as a good guide to some common (and uncommon) configuration requirements.

HTH
--
Lew Pitcher
"In Skills, We Trust"

On 2022-01-26, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
> mailx -s "Test results" me@my.domain.invalid <<EOT
> message to deliver
> ...
> EOT
>
> Now on Linux/Ubuntu I get that error
>
> WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
> No such file or directory
> send-mail: Authorization failed (535 Incorrect authentication data)
> Can't send mail: sendmail process failed with error code 1

Very strange. Maybe some unusual crontab variables set?

On 26.01.2022 16:36, Fenris wrote:
> On 2022-01-26, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
>> mailx -s "Test results" me@my.domain.invalid <<EOT
>> message to deliver
>> ...
>> EOT
>>
>> Now on Linux/Ubuntu I get that error
>>
>> WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
>> No such file or directory
>> send-mail: Authorization failed (535 Incorrect authentication data)
>> Can't send mail: sendmail process failed with error code 1
>
> Very strange. Maybe some unusual crontab variables set?

This error was just the result of a try from the command line, no cron
involved here.

Thanks also for the other replies thus far.

Janis

On 26.01.2022 15:39, Dan Espen wrote:
> Janis Papanagnou <janis_papanagnou@hotmail.com> writes:
>
>> Decades ago I used (on AIX) the 'mailx' command to automatically send
>> notifications from cron'd shell scripts per email, [...]
>
> It's not email, but notify-send works if you want the message routed to
> the desktop.

I've also thought about such an alternative, e.g. I had used 'zenity'
(a similar tool) for notifications in one case before.

An email interface would open a broader applicability, though, thus
still searching...

Janis

On 26.01.2022 15:59, Lew Pitcher wrote:
> On Wed, 26 Jan 2022 15:20:04 +0100, Janis Papanagnou wrote:
>
> [snip]
>> [*] I've heard that sendmail configuration is a nightmare.
>
> Sendmail configuration is indeed complex, mostly due to the
> archaic form of it's configuration file, and the variety of options
> available for mail handling.
> [...]

My preference would be to not have to touch it, if avoidable.

Working tools solutions would certainly be nice, if existing.

Janis

On 2022-01-26 09:20, Janis Papanagnou wrote:
> Decades ago I used (on AIX) the 'mailx' command to automatically send
> notifications from cron'd shell scripts per email, something like
>
> mailx -s "Test results" me@my.domain.invalid <<EOT
> message to deliver
> ...
> EOT
>
> Now on Linux/Ubuntu I get that error
>
> WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
> No such file or directory
> send-mail: Authorization failed (535 Incorrect authentication data)
> Can't send mail: sendmail process failed with error code 1
>
> Two questions:
> * Where do I have to look (or what to do)[*] to fix that problem?
> * Is there some other (preferred, simpler, or without crypto demands)
> interface or tool to send emails automatically from a shell script?

Be aware that on Ubuntu, "sendmail" may not actually be the original
sendmail program. Almost all Message Transfer Agents (MTAs) install a
/usr/bin/sendmail program or symlink. I believe the default on Ubuntu
is actually Postfix.

I use Debian with (the default) Exim as the MTA, and mailx has always
worked out of the box for me. No gnome-keyring involved. So your
problem might be specific to Ubuntu.

Either alt.os.linux.ubuntu or comp.os.linux.misc might have more answers.

On Wed, 26 Jan 2022 17:12:22 +0100, Janis Papanagnou wrote:

> On 26.01.2022 16:36, Fenris wrote:
>> On 2022-01-26, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
>>> mailx -s "Test results" me@my.domain.invalid <<EOT
>>> message to deliver
>>> ...
>>> EOT
>>>
>>> Now on Linux/Ubuntu I get that error
>>>
>>> WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
>>> No such file or directory
>>> send-mail: Authorization failed (535 Incorrect authentication data)
>>> Can't send mail: sendmail process failed with error code 1
>>
>> Very strange. Maybe some unusual crontab variables set?
>
> This error was just the result of a try from the command line, no cron
> involved here.
>
> Thanks also for the other replies thus far.
>
> Janis

From what I've been able to gather, mailx(1) invokes sendmail(1) under
the covers. On my Slackware system, mailx(1) /does not/ have any hardcoded
references to gnome-keyring, or any other keyring, for that matter.

I do note that the mailx(1) manpage states:
Sending mail from scripts
If you want to send mail from scripts, you must be aware that mailx
reads the user's configuration files by default. So unless your script
is only intended for your own personal use (as e.g. a cron job), you
need to circumvent this by invoking mailx like

MAILRC=/dev/null mailx -n

You then need to create a configuration for mailx for your script.
This can be done by either pointing the MAILRC variable to a custom
configuration file, or by passing the configuration in environment
variables. Since many of the configuration options are not valid shell
variables, the env command is useful in this situation. An invocation
could thus look like

env MAILRC=/dev/null from=scriptreply@domain smtp=host \
smtp-auth-user=login smtp-auth-password=secret \
smtp-auth=login mailx -n -s "subject" \
-a attachment_file recipient@domain <content_file

Perhaps the default MAILRC for /your/ invocation of mailx(1) contains some
reference to a cryptographic signature that, as a byproduct, attempts to invoke
the system keyring to determine the proper keys. This is where I'd start looking.

HTH
--
Lew Pitcher
"In Skills, We Trust"

On 2022-01-26, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
>>> WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
>>> No such file or directory
>>> send-mail: Authorization failed (535 Incorrect authentication data)
>>> Can't send mail: sendmail process failed with error code 1
>>
>> Very strange. Maybe some unusual crontab variables set?
>
> This error was just the result of a try from the command line, no cron
> involved here.

Maybe running `killall gnome-keyring-daemon' before the command?

Just to approach that "gnome-keyring" is the problem but not sendmail etc.

Janis Papanagnou <janis_papanagnou@hotmail.com> schrieb:
> On 26.01.2022 16:36, Fenris wrote:
>> On 2022-01-26, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:

Hello Janis!

>>> mailx -s "Test results" me@my.domain.invalid <<EOT
>>> message to deliver
>>> ...
>>> EOT
>>>
>>> Now on Linux/Ubuntu I get that error
>>>
>>> WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
>>> No such file or directory
>>> send-mail: Authorization failed (535 Incorrect authentication data)
>>> Can't send mail: sendmail process failed with error code 1
>>
>> Very strange. Maybe some unusual crontab variables set?
>
> This error was just the result of a try from the command line, no cron
> involved here.
>
I have two points.

a) How does "normal" mail sending works?
Does it invoke sendmail?
I guess not. Otherwise you should observe the same errors.

b) More and more mail provider insist on encrypted transport.
May be in the past the sendmail configuration regarding encryption
has never been invoked. But now it is a problem.

You could consider to use more simple replacements for sendmail.
One is msmtp just for outgoing mail to a smart host.
Please see https://wiki.debian.org/msmtp for an overview.
It lists also alternatives.

The Dragonfly Mail Agent dma is also a simple
sendmail replacement. I am not sure if there is a Debian or Ubuntu
package.

I think the easiest approach is to start with msmtp or similar.

Kind regards,
Christoph

On 26/01/2022 14:20, Janis Papanagnou wrote:
> Decades ago I used (on AIX) the 'mailx' command to automatically send
> notifications from cron'd shell scripts per email, something like
>
> mailx -s "Test results" me@my.domain.invalid <<EOT
> message to deliver
> ...
> EOT
>
> Now on Linux/Ubuntu I get that error
>
> WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
> No such file or directory
> send-mail: Authorization failed (535 Incorrect authentication data)
> Can't send mail: sendmail process failed with error code 1
>
> Two questions:
> * Where do I have to look (or what to do)[*] to fix that problem?
> * Is there some other (preferred, simpler, or without crypto demands)
> interface or tool to send emails automatically from a shell script?
>
> Thanks for any insights.
>
> (References to more appropriate newsgroups are also welcome.)
>
> Janis
>
> [*] I've heard that sendmail configuration is a nightmare.
>

Do you want to send mail to your real email address
janis_pxxxxxxxx@hotmail.com?
Or just to your local user?
For the first look at https://github.com/deanproxy/eMail

--
Chris Elvidge
England

On 2022-01-26 11:12, Janis Papanagnou wrote:
> On 26.01.2022 16:36, Fenris wrote:
>> On 2022-01-26, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
>>> mailx -s "Test results" me@my.domain.invalid <<EOT
>>> message to deliver
>>> ...
>>> EOT
>>>
>>> Now on Linux/Ubuntu I get that error
>>>
>>> WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
>>> No such file or directory
>>> send-mail: Authorization failed (535 Incorrect authentication data)
>>> Can't send mail: sendmail process failed with error code 1
>>
>> Very strange. Maybe some unusual crontab variables set?
>
> This error was just the result of a try from the command line, no cron
> involved here.

In that case, check your environment for any GNOME_KEYRING_* variables.
If there are any, unset them and re-try your mailx command.

On 2022-01-26, Lew Pitcher <lew.pitcher@digitalfreehold.ca> wrote:
> On Wed, 26 Jan 2022 15:20:04 +0100, Janis Papanagnou wrote:
>
> [snip]
>> [*] I've heard that sendmail configuration is a nightmare.
>
> Sendmail configuration is indeed complex, mostly due to the
> archaic form of it's configuration file, and the variety of options
> available for mail handling.

Many distributions now use postfix as the mail sender/receiver, not
sendmail. It has a "sendmail" stub to make software think that it is
sendmail that is being used. Check what you are using first.

On 26.01.2022 18:28, John-Paul Stewart wrote:
> On 2022-01-26 11:12, Janis Papanagnou wrote:
>> On 26.01.2022 16:36, Fenris wrote:
>>> On 2022-01-26, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
>>>> mailx -s "Test results" me@my.domain.invalid <<EOT
>>>> message to deliver
>>>> ...
>>>> EOT
>>>>
>>>> Now on Linux/Ubuntu I get that error
>>>>
>>>> WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
>>>> No such file or directory
>>>> send-mail: Authorization failed (535 Incorrect authentication data)
>>>> Can't send mail: sendmail process failed with error code 1
>>>
>>> Very strange. Maybe some unusual crontab variables set?
>>
>> This error was just the result of a try from the command line, no cron
>> involved here.
>
> In that case, check your environment for any GNOME_KEYRING_* variables.
> If there are any, unset them and re-try your mailx command.

There are two such variables. Clearing or unset'ing them for the mailx
command has no effect, though; same error...

send-mail: Authorization failed (535 Incorrect authentication data)
Can't send mail: sendmail process failed with error code 1

Janis

On 2022-01-26, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
> On 26.01.2022 18:28, John-Paul Stewart wrote:
>> On 2022-01-26 11:12, Janis Papanagnou wrote:
>>> On 26.01.2022 16:36, Fenris wrote:
>>>> On 2022-01-26, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
>>>>> mailx -s "Test results" me@my.domain.invalid <<EOT
>>>>> message to deliver
>>>>> ...
>>>>> EOT
>>>>>
>>>>> Now on Linux/Ubuntu I get that error
>>>>>
>>>>> WARNING: gnome-keyring:: couldn't connect to: /tmp/keyring-.../pkcs11:
>>>>> No such file or directory
>>>>> send-mail: Authorization failed (535 Incorrect authentication data)
>>>>> Can't send mail: sendmail process failed with error code 1
>>>>
>>>> Very strange. Maybe some unusual crontab variables set?
>>>
>>> This error was just the result of a try from the command line, no cron
>>> involved here.
>>
>> In that case, check your environment for any GNOME_KEYRING_* variables.
>> If there are any, unset them and re-try your mailx command.
>
> There are two such variables. Clearing or unset'ing them for the mailx
> command has no effect, though; same error...
>
> send-mail: Authorization failed (535 Incorrect authentication data)
> Can't send mail: sendmail process failed with error code 1

Figure out what your MTA (Mail transfer agent) is. Is it really sendmail, or is it something
like postfix?
Eg on my system (Mageia not Ubuntu):

tunnel:1.0[unruh]>l /sbin/sendmail
lrwxrwxrwx 1 root root 34 Apr 12 2019 /sbin/sendmail -> /etc/alternatives/sendmail-command
l /etc/alternatives/sendmail-command
lrwxrwxrwx 1 root root 26 Apr 12 2019 /etc/alternatives/sendmail-command -> /usr/sbin/sendmail.postfix

(l is an alias for ls -la)

Does regular mail work? What do you use as your normal mailer-- not
mailx I presume. What MTA does it use? It is still working?

>
> Janis
>

On 26.01.2022 19:18, William Unruh wrote:
>
> Figure out what your MTA (Mail transfer agent) is. Is it really sendmail, or is it something
> like postfix?
> Eg on my system (Mageia not Ubuntu):
>
> tunnel:1.0[unruh]>l /sbin/sendmail
> lrwxrwxrwx 1 root root 34 Apr 12 2019 /sbin/sendmail -> /etc/alternatives/sendmail-command
> l /etc/alternatives/sendmail-command
> lrwxrwxrwx 1 root root 26 Apr 12 2019 /etc/alternatives/sendmail-command -> /usr/sbin/sendmail.postfix

/usr/sbin/sendmail -> ssmtp

The latter is an executable file.

>
> Does regular mail work? What do you use as your normal mailer-- not
> mailx I presume. What MTA does it use? It is still working?

Yes, as the standard email application I use a Thunderbird client.
As outgoing server there's one at my ISP defined, dedicated to my
account; I haven't configured anything else when I had set it up.

Thinking about it; how would 'mailx' know that outgoing server?
It must be defined somewhere, I suppose.

Janis

On Wed, 26 Jan 2022 20:30:33 +0100, Janis Papanagnou wrote:

> On 26.01.2022 19:18, William Unruh wrote:
>>
>> Figure out what your MTA (Mail transfer agent) is. Is it really sendmail, or is it something
>> like postfix?
>> Eg on my system (Mageia not Ubuntu):
>>
>> tunnel:1.0[unruh]>l /sbin/sendmail
>> lrwxrwxrwx 1 root root 34 Apr 12 2019 /sbin/sendmail -> /etc/alternatives/sendmail-command
>> l /etc/alternatives/sendmail-command
>> lrwxrwxrwx 1 root root 26 Apr 12 2019 /etc/alternatives/sendmail-command -> /usr/sbin/sendmail.postfix
>
> /usr/sbin/sendmail -> ssmtp
>
> The latter is an executable file.
>
>>
>> Does regular mail work? What do you use as your normal mailer-- not
>> mailx I presume. What MTA does it use? It is still working?
>
> Yes, as the standard email application I use a Thunderbird client.
> As outgoing server there's one at my ISP defined, dedicated to my
> account; I haven't configured anything else when I had set it up.
>
> Thinking about it; how would 'mailx' know that outgoing server?
> It must be defined somewhere, I suppose.

mailx (a MUA, or "Mail User Agent") hands it's outgoing email to
postfix (a MTA, or "Mail Transfer Agent") by forking off a child
that runs "sendmail" (in your case, a softlink to postfix).

This sendmail/postfix child process passes the email on to the
next MTA (usually, the email MTA daemon running on your network),
which, in turn, passes the email onward to the receiver. Note that
the postfix child process /can/ transfer the email onward towards
the recipient(s) without a local email MTA daemon.

If you haven't configured postfix to relay email via your ISP's
email server, then it likely tries to deliver the email directly.
Check your system's /etc/postfix/main.cf configuration file for
all the gruesome details.

HTH
--
Lew Pitcher
"In Skills, We Trust"

On 26.01.2022 20:45, Lew Pitcher wrote:
>
> If you haven't configured postfix to relay email via your ISP's
> email server, then it likely tries to deliver the email directly.
> Check your system's /etc/postfix/main.cf configuration file for
> all the gruesome details.

Hmm.. - beneath /etc I neither found a file or directory named
postfix nor a file main.cf.

Janis

PS: I haven't yet worked through all the posted suggestions and
hints, so I still have to do some homework here...

On 2022-01-26, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
> On 26.01.2022 20:45, Lew Pitcher wrote:
>>
>> If you haven't configured postfix to relay email via your ISP's
>> email server, then it likely tries to deliver the email directly.
>> Check your system's /etc/postfix/main.cf configuration file for
>> all the gruesome details.
>
> Hmm.. - beneath /etc I neither found a file or directory named
> postfix nor a file main.cf.
>
> Janis
>
> PS: I haven't yet worked through all the posted suggestions and
> hints, so I still have to do some homework here...

Didn't I see you reference something called "ssmtp" ?
That's a program for sending email. So "man ssmtp" should give you more info.
Also try this page...

https://linuxhandbook.com/linux-send-email-ssmtp/

If I recalled wrongly, then apologies for the noise.

On 1/26/22 7:59 AM, Lew Pitcher wrote:
> Sendmail configuration is indeed complex, mostly due to the archaic
> form of it's configuration file, and the variety of options available
> for mail handling.

As much as I might not like it, I agree with this statement.

> However, depending on your distro, your installation may have come
> with one or more sample configurations, most of which are relatively
> easy to modify for use.

I don't think I've used distribution provided templates before. I
usually use the generic templates that come with the (various) Sendmail
(cf|config) package(s).

> I personally run sendmail as my public MTA, with some custom config
> changes to handle miltering (raw email filtering) and secured outbound
> email relaying (through my ISP's MTA). My sendmail.mc file runs 22
> lines (excluding comments), and only differs from my distro's stock
> sendmail.mc by 4 lines.

I also run Sendmail, by choice, as my MTA.

> FWIW, I can recommend
> "sendmail"
> by Bryan Costales with Eric Allman
> O'Reilly & Associates
> ISBN 1-56592-222-0
> as a /really/ good book on the subject, and
> "sendmail Cookbook"
> by Craig Hunt
> O'Reilly & Associates
> ISBN 0-596-00471-0
> as a good guide to some common (and uncommon) configuration requirements.

I'm sure those are wonderful sources of Sendmail information. However
I'm quite certain that I would definitely *NOT* recommend that someone
who simply wants to get an MTA function to send email read them. I
would, and have, recommended both of them to someone who wanted to learn
more about Sendmail specifically.

These books fall into the category of telling you how to build a clock
before telling what time to set it to.

--
Grant. . . .
unix || die

On 1/26/22 9:33 AM, Fenris wrote:
> Maybe running `killall gnome-keyring-daemon' before the command?

I would avoid doing that.

Especially if you're using the gnome-keyring-daemon as the ssh agent
managing keys.

This suggestion seems akin to a scream test to me.

> Just to approach that "gnome-keyring" is the problem but not sendmail etc.

I don't think that the Gnome keyring, nor Sendmail (the program) is the
OPs problem.

--
Grant. . . .
unix || die

On 1/26/22 9:28 AM, John-Paul Stewart wrote:
> Be aware that on Ubuntu, "sendmail" may not actually be the original
> sendmail program. Almost all Message Transfer Agents (MTAs) install
> a /usr/bin/sendmail program or symlink.

The sendmail (executable) has become a defacto command line interface
for sending email, be it the actual Sendmail (program) or Postfix
(program) or something else.

I consider the sendmail (executable) to be (ab)used in the same way as
an API.

--
Grant. . . .
unix || die

William Unruh <unruh@invalid.ca> writes:
[...]
> Figure out what your MTA (Mail transfer agent) is. Is it really sendmail, or is it something
> like postfix?
> Eg on my system (Mageia not Ubuntu):
>
> tunnel:1.0[unruh]>l /sbin/sendmail
> lrwxrwxrwx 1 root root 34 Apr 12 2019 /sbin/sendmail -> /etc/alternatives/sendmail-command
> l /etc/alternatives/sendmail-command
> lrwxrwxrwx 1 root root 26 Apr 12 2019 /etc/alternatives/sendmail-command -> /usr/sbin/sendmail.postfix
>
> (l is an alias for ls -la)

On my Ubuntu 20.04 system:

$ type sendmail
sendmail is /usr/sbin/sendmail
$ ls -l /usr/sbin/sendmail
-rwxr-xr-x 1 root root 35128 Sep 6 23:58 /usr/sbin/sendmail
$ dpkg -S /usr/sbin/sendmail
postfix: /usr/sbin/sendmail
$·

The point being that just listing the sendmail executable might not tell
you what it is. ("dpkg -S" tells you what package provides a given
file. You'll need to use some other command on a system that's not
Debian-based.)

--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips
void Void(void) { Void(); } /* The recursive call of the void */

On 2022-01-26, Janis Papanagnou <janis_papanagnou@hotmail.com> wrote:
> On 26.01.2022 19:18, William Unruh wrote:
>>
>> Figure out what your MTA (Mail transfer agent) is. Is it really sendmail, or is it something
>> like postfix?
>> Eg on my system (Mageia not Ubuntu):
>>
>> tunnel:1.0[unruh]>l /sbin/sendmail
>> lrwxrwxrwx 1 root root 34 Apr 12 2019 /sbin/sendmail -> /etc/alternatives/sendmail-command
>> l /etc/alternatives/sendmail-command
>> lrwxrwxrwx 1 root root 26 Apr 12 2019 /etc/alternatives/sendmail-command -> /usr/sbin/sendmail.postfix
>
> /usr/sbin/sendmail -> ssmtp

So it seems that you use ssmtp as your MTA. That is supposed to be a
simple message transfer agent.
It appears to have its setup in /etc/ssmtp/ssmtp.conf, which probably
includes the server. It may be that it only uses the server if the mail
is not local mail (in fact the server could not handle local mail at all
anyway, as it is probably on its own private network hidden from the
outside world). Thus ssmtp tries to send it to a local machine, and that
machine is not running ssl for the mail receiving, and it thus craps
out. This is all a guess, since I have no idea how ssmtp world or what
your network topology is or almost anything else about your system.

>
> The latter is an executable file.
>
>>
>> Does regular mail work? What do you use as your normal mailer-- not
>> mailx I presume. What MTA does it use? It is still working?
>
> Yes, as the standard email application I use a Thunderbird client.
> As outgoing server there's one at my ISP defined, dedicated to my
> account; I haven't configured anything else when I had set it up.
>
> Thinking about it; how would 'mailx' know that outgoing server?
> It must be defined somewhere, I suppose.
>
> Janis
>