Errors with SMTP when sending mail

[guillaumesoucy]

Good day!

When I try to send a message with Roundcube I got this error: in the right bottom page. And also when trying to use Mozilla Thunderbird it gave me these errors: and

Postfix and Dovecote are installed and up-to-date on the server running Ubuntu 20.04 LTS x64. I'd take the instructions from https://www.vultr.com/docs/how-to-install-postfix-dovecot-and-roundcube-on-ubuntu-20-04#3__Install___Configure_Dovecot but SMTP seem not working. What I'd need to to to get it work?

Thanks,

Guillaume

[JohnDoh]

The fact you get errors from both Roundcube and Thunderbird suggests a problem with your SMTP server. You say you are using Postfix if you are not sure what is wrong then I suggest you ask in the Postfix community as here we can only give advice about Roundcube.