SMTP configuration without encryption

I try to configure SMTP without encryption, I can’t do it
ubuntu 22.04 LTS
Nextcloud 27.1.3
How to do? Thanks

Any help?
I use a postfix mail server, I do not use SSL or STARTLS. Nextcloud is configured in https with letsencrypt.
the mail_debug parameter gives no trace.
I have an earlier version of Nextcloud which is configured in the same way and which sends emails to the same postfix server and the emails arrive well.
but with version 27.1.3, I cannot configure sending emails without SSL or STARTLS.
In the postfix mail server logs, I have a message: as if the nextcloud SMTP configuration is in SSL

"SSL_accept error from unknown[x.y.y.a ]: -1
postfix/smtpd[4314]: warning: TLS library problem: error:14094418:SSL routines:ssl3_read_bytes:tlsv1 alert unknown ca:…/ssl/record/rec_layer_s3.c:1543:SSL alert number 48:

Please provide the output of occ config:list system.

If you do not want to use encryption, your SMTP servers needs to not advertise support for STARTTLS. NC only uses it if it’s offered.

The correct mode is None/STARTTLS from the sounds of your situation.

If it worked with older versions of NC it was because the old implementation in NC ignored STARTTLS when it was offered by your email server.

Alternatively, you can determine why it’s failing when encrypted. It should work even encrypted, but if it is self signed you’ll need to add this to your config.php:

For debugging, you’ll need to change your log level too as described here: