Question How To Setup Outgoing Only Mail

[X3Web]

Server operating system version

Ubuntu 20.04.6 LTS

Hi,

We have a client using MS Exchange for their email, but they want a separate "scans" email that only sends messages through my server. When I enable the mail service for this domain, it works, but if they try to send emails to the same domain, it fails because the system tries to deliver locally.

If I disable incoming mail to avoid this, the "scans" email can’t authenticate and throws the following error:

"Oct 24 11:05:57 hosting plesk_saslauthd[2172378]: failed mail authentication attempt for user '[email protected]' (password len=10)"

Can anyone help me fix this? It seems like the server isn’t allowing SMTP for authentication, or maybe I’m missing something.

 

[scsa20]

You might want to remove your license key since that isn't your plesk version. Also make sure you are on the latest version of Plesk since the latest version has the option for the domain's email settings of "Disabled for incoming mail" which allows you to use as sending but not getting emails and should work as expected.

 

[george-the-guy]

any update on this, when i check "Disable for incoming mail" SMTPS fails for all mailboxes on that domain.
errors below

2024-11-25 13:06:40	warning	postfix/smtpd [24575]	warning: serverdomain.com[xx.xx.xx.xx]: SASL CRAM-MD5 authentication failed: authentication failure, sasl_username=[email protected]
2024-11-25 13:06:40	warning	postfix/smtpd [24575]	warning: SASL authentication failure: no secret in database

it is required due to a nightmare set of client requirements to force emails to look outside the server as the MX record doesnt point at this server.

 

[scsa20]

Are you using the DNS server for that domain on the server as well or are you using an external DNS server? If you're using an external DNS server make sure the DNS service is turned off on the domain or make sure that the MX record on there is pointing to the MX server you're trying to route emails to should fix the issue.

 

[george-the-guy]

When doing either of the suggested options, i get the following error

postfix/smtpd Recipient address rejected: User unknown in virtual mailbox table

it seems like it may be a postfix related problem, any suggestions welcome this problem has been haunting me for too long

im attempting to use a catch all forwarder alongside this to hopefully get the desired result

 

[george-the-guy]

Update - Still hits the postfix mailtable and fails