no authentication for incoming mail on sendmail, linux (debian) [closed]

StackOverflow https://stackoverflow.com/questions/21469971

  •  05-10-2022
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Question

I have installed sendmail on my webserver. Sending and receiving emails does work, but when I use authentication on port 25 ( to avoid spam attacks), I can't receive emails anymore. All I get is an authentication error.

Is there a way to deactivate authentication in sendmail for incoming mail?

Edit 1 : In my sendmail configuration I have this lines: 

DAEMON_OPTIONS(Name=ESMTP,Port=465,Modifiers=a')
DAEMON_OPTIONS(Name=STARTTLS,Port=587,Modifiers=a') 
DAEMON_OPTIONS(`Name=SMTP,Modifiers=a')
Was it helpful?

Solution

You can not force authentication on port SMTP (25) if you want to receive messages from "strangers" (other SMTP hosts worldwide).

You should require authentication on SMTPS (465) and MSA (587) ports.

You may reject connection from DUL (dynamically allocated) IP addresses for unauthenticated connections and addresses listed by other DNSBL lists. Use FEATURE(enhdnsbl,...) with some DNSBL listing DUL ranges and FEATURE(delay_checks,...).

BTW You have missed s Modifier for SMTPS.

DAEMON_OPTIONS(`Name=SMTPS,Port=465,Modifiers=sa')
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