Seperating SMTP and POP/IMAP services

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Seperating SMTP and POP/IMAP services
\ David Sharpe (8 May 2008)
. \ Victor Duchovni (8 May 2008)
. . \ David Sharpe (8 May 2008)
. \ Bill Cole (8 May 2008)
. . \ David Sharpe (8 May 2008)
. . . \ Bill Cole (8 May 2008)

3 msg	Test 2
1 msg	Testing
12 msg	[Fwd: ldap users & aliases config]

Subject:	Seperating SMTP and POP/IMAP services
Group:	Postfix-users
From:	David Sharpe
Date:	8 May 2008

Hi,

I have 2 instances of Postfix running on the same machine:

mail.domain.com handles incoming email and forwarded email
smtp.domain.com handles outgoing email

Users are instructed to use the smtp.domain.com for their outgoing
server, however some do not.
So I want to prevent these users from sending email over mail.domain.com
(wishlist: with a friendly message
which says please use smtp.domain.com).

What is the cleanest way of breaking this type of SMTP usage on
mail.domain.com whilst still allowing it to forward email.

Thanks,
David