Unable to get Zoho Mail Working with Mattermost for SMTP

Troubleshooting
1

Hey there,

I use the free zoho mail account that allows 5 emails. I created an email with noreply@mydomain.com for mattermost to use to send communications, password resets for self service etc. I also self-host mattermost and have it spun up using Easypanel. Version 8.1.7 intentionally to use the board functionality.

I went into the SMTP settings and I am entering the following following the instructions from Zoho, but I do not see any successful connections.

SMTP Server: smtppro.zoho.com
SMTP Server Port: 587
Enable SMTP Auth: tue
SMTP server username: noreply@mydomain.com
SMTP Server Password: my 60 character random password
Connection Security: TLS (recommended)
Skip Server Cert. Verification: false
Enable security alerts: true

Output on test connection:
Connection unsuccessful: Connection unsuccessful: unable to connect to the SMTP server through TLS: tls: first record does not look like a TLS handshake

When I change the Connection Security to None and port to 465 (SSL) and attempt to test the connection, I get the following output:
Connection unsuccessful: Connection unsuccessful: unable to connect to the SMTP server: context deadline exceeded

I would appreciate any input from folks who have set up their Zoho emails to provide mattermost communications on the platform (like password reset using noreply). I am not sure why it is not connecting as I assume it should. I will post solution if I solve the issue as well, however, this has been a challenge for several hours now.

Thanks.

2

This has been solved. Following configs work.

SMTP Server: http://smtppro.zoho.com/
SMTP Server Port: 587
Enable SMTP Auth: true
SMTP server username: noreply@mydomain.com
SMTP Server Password: my 60 character random password
Connection Security: STARTTLS
Skip Server Cert. Verification: false
Enable security alerts: true

3

This isn’t working for me as of mattermost/mattermost-team-edition:release-10.

Using 587 with STARTTLS, getting the error Connection unsuccessful: Connection unsuccessful: failed to close connection to the SMTP server: 553 Relaying disallowed as @

Per Zoho docs, it’s bad credentials, however, I’m using the exact same credentials for all other self-hosted apps.

Am I missing something else, or have there, perhaps, been other reversions or breaking changes?

4

“Relaying denied” means the SMTP server you’re connecting to isn’t going to deliver mail destined for non-local accounts. It has nothing to do with Mattermost or credentials.

5

Appreciate the feedback. The thing is, those very same credentials work in all other apps (via the same Coolify instance). Penpot, Nextcloud, Plane, etc. all work. Mattermost is the only one that doesn’t.

I did some fiddling to reproduce the error by other means (e.g. curl) and it appears that (in the case of Zoho) 553 often stems from a bad or nonexistent FROM. If I attempt to send from do-not-reply-to-this@mydomain.com and that isn’t a real email address, it will be rejected. If I switch it to a proper email address, everything is fine. Is Mattermost providing a proper FROM during email attempts?

6

That’s a fair question! You could point it at a mail server you control, initiate an email, and see what it says. I may try that and see what happens. I would submit that the validity of a FROM address really isn’t a good test for relaying, as you can make it say anything you want. You probably get emails from do_not_reply@example.xyz