As I have been trying to use Roundcube, I have unfortunately encountered a variety of problems.
One serious problem has been a complete failure to send any outgoing messages.
When it is attempted to send a message from the composition pane (by clicking the button Send), no action is completed, instead only is briefly flashed, in the lower right corner of the pane, the following error message:
SMTP Error (): Connection to server failed.
Despite that my testing so far has been quite limited, I recall at least having some previous success in sending basic outgoing messages.
Additionally, forwarded messages have reached their destinations, through the same channels.
I would like help resolving the cause of the 'SMTP Error".
Notes
It is possible that the more suitable category would be Support apps, in comparison to Support.
Additionally, the problem as reported seems to be a duplicate of the topic referenced below, but no resolution has been offered that preserves the model of low-level administration being subsumed under the broader automated framework of Yunohost.
Could you check that the domain setting mail_out is activated Web Admin > Domains > XXXX.tld > Outgoing emails ?
You probably should open the mail log (see bellow) and retry to send a mail with roundcube to see if something appears in the log:
tail -f /var/log/mail.log
(do CTRL + C to terminate this command)
I hope this answer was helpful. Please keep in mind that most of YunoHost’s development is done by volunteers, including this answer. Some of them earn less than the minimum wage in their country. If you can afford it, please consider donating to the 2026 fundraising campaign to help us keep this project going without putting anyone at risk.
I can confirm that outgoing mail is enabled for the domain, based on reviewing the configuration menus to which you referred.
Thank you, also, for your suggestion to review the mail log.
Unfortunately, I find nothing of interest relating to my attempt to send a message through Roundcube:
As follows is a (redacted) except of /var/log/mail.log:
postfix/submission/smtpd[146179]: connect from unknown[1234:abcd::]
postfix/submission/smtpd[146179]: TLS SNI yunohost.example.tld from unknown[1234:abcd::] not matched, using default chain
postfix/submission/smtpd[146179]: Anonymous TLS connection established from unknown[1234:abcd::]: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (4096 bits) server-digest SHA256
postfix/submission/smtpd[146179]: NOQUEUE: lost connection after STARTTLS from unknown[1234:abcd::]
postfix/submission/smtpd[146179]: disconnect from unknown[1234:abcd::] ehlo=1 starttls=1 commands=2