[BlueOnyx:26345] Re: 5210R sendmail to postfix switch questions

[Michael Stauber]

Hi Tim,

> 5210R
> 
> I am pondering switching from sendmail to postfix.
> 
> Anything that I should be aware of with regard to what is going to 
> change regarding my client's email client setups?
> 
> Is there anything that they will have to change in their settings?
> 
> Can I switch back if I suddenly run into issues (my clients)

On 5210R/5211R you can switch between Sendmail and Postfix at any time 
and in either direction. Typically the clients won't even notice and no 
config changes are required server side or client side.

The main difference between Sendmail and Postfix (as far as BlueOnyx 
goes) is this:

Postfix supports SNI. So it will make use of *all* SSL certificates. 
That includes the GUI's cert and the SSL cert of all Vsites that have 
SSL enabled.

Whereas Sendmail could only use a single SSL certificate and therefore 
only used the GUI's SSL cert.

With Postfix your clients (who have SSL enabled on their Vsite) no 
longer get an SSL certificate mismatch if they use SMTPS, POPS or IMAPS 
and their configured mail-endpoint on the BlueOnyx is the domain name of 
their Vsite.

Of course: If you ever have clients who use *that* setup and switch back 
from Postfix to Sendmail? Yeah, then they get the "certificate mismatch" 
again, because Sendmail only uses the GUI cert, which doesn't have 
provisions for any Vsite SSL.

Other than that? Postfix is more robust and takes abuse a lot better 
than Sendmail. The way we have Postfix set up on BlueOnyx is that each 
time when Postfix is started it parses the Sendmail configuration and 
creates a new Postfix configuration on the fly. That way the 
configuration of both MTAs remains identical and "doesn't drift apart".

Should you ever wish to configure Postfix differently than the GUI 
allows, or want to set a parameter that the GUI doesn't have for the 
Postfix configuration? You can put your changes into this script, which 
will never be overwritten by YUM updates:

/usr/sausalito/bin/custom-postfix-confgen.sh

There is an example in that file that shows how it's done. This script 
runs at the end of the auto-configure of Postfix that happens during 
each Postfix restart. So you have full flexibility of how you want to 
configure that service if you want to tweak it further than the GUI allows.

Let me know if you have any further questions and I'd be glad to help.

-- 
With best regards

Michael Stauber