Re: [Fetchmail-users] Local delivery - smtp or sendmail

[Hans C. <fo...@gm...>]

On Tue, 11 Nov 2025, Matthias Andree via Fetchmail-users wrote:

> Am 09.11.25 um 01:50 schrieb Hans Carlson via Fetchmail-users:
>>
>>  I'm trying to configure smtpd_sender_restrictions in postfix, mainly so
>>  I'll get an immediate failure if I've added a new email address that
>>  hasn't been configured in postfix.
>
> Those are only available through SMTP, not through most 
> /usr/{lib,sbin}/sendmail wrappers (certainly not Postfix's).

Right, the restrictions I was planning to configure would only apply to 
the smtp connections from alpine.  I don't think I want any restrictions 
on the connections from fetchmail.  fetchmail should process all the mail 
it gets and deliver it to the local user.

For the smtp connections from alpine on the other hand I want to add a 
simply table with a list of the email addresses that are allowed to send 
email.  If in the future I add a new email address, then I want the alpine 
SMTP connection to my local postfix SMTP server to give me an immediate 
rejection so I know I need to go configure authentication for the new 
email address.  Without that, the postfix SMTP client connection to the 
isp relay will eventually fail with an auth error, but I won't notice it 
for some time because that's all done in the background.

Sooo... if I don't actually want any restrictions on fetchmail, then is 
there any reason NOT to use sendmail for delivery instead of SMTP?

>>  The problem is, if I add smtp_sender_restrictions in the postfix config
>>  (main.cf), then those restrictions apply to all connections; both from
>>  alpine and fetchmail.  I'm fairly certain there's a way to distinguish
>>  this by adding something to master.cf (still figuring that part out), but
>>  the key is, there needs to be a way to distinguish between the two.  I
>>  think if fetchmail uses sendmail instead of smtp, I can use that to setup
>>  restrictions based on smtp connections (alpine/outbound) and restrictions
>>  based on sendmail connections (fetchmail/inbound).
>
> You can add another smtpd listener (right hand side of master.cf) in Postfix 
> on a different port (left-hand side of master.cf, you can also give numbers 
> of ports instead of service names) and configure that with its own option 
> set. If you indent 2nd, 3rd, ... lines Postfix reads them as continuation of 
> the previous line in master.cf, and it should have relevant examples.

Yes, that is the other option I was looking at.  But using sendmail 
instead of a separate smtpd listener seemed like the simpler option as 
long as I don't need/want any local processing of inbound email by smtpd. 
Maybe in the future I'll think of something, but for right now I don't 
think smtpd would be adding anything to the process... basically, I just 
want fetchmail to get the mail and get it to the users INBOX.

And if I do want to process the incoming mail in some way in the future, I 
was planning to investigate some combination of postfix, dovecot and 
sieve.  At this point I don't really know anything about that, other than 
it seems to be possible.