Copying settings in main.cf from postfix 3.5.6 to postfix 3.3.0 - any major issues?

[Chris Green-11]

I currently have mail for [hidden email] and [hidden email] forwarded
by my hosting service to a Postfix server on my desktop machine (which
is zbmc.eu).  The Postfix configuration is fairly simple, just accepts
mail for the zbmc.eu domain and sends mail via my hosting service's
smarthost.

I want to create a similar Postfix server installation on a VPS I
already run so that if my home desktop machine has a long down time
for any reason I can forward my mail from my hosting provider to the
VPS instead.  This is a simple reconfiguration on my hosting provider.

The VPS has postfix version 3.3, my desktop has version 3.5.6, am I
likely to encounter any problems with a similar main.cf on the older
version?  I realise I have to change the myorigin, mydestination and
myhostname but I'm hoping that's basically all.

--
Chris Green

[Wietse Venema]

Chris Green:

> I currently have mail for [hidden email] and [hidden email] forwarded
> by my hosting service to a Postfix server on my desktop machine (which
> is zbmc.eu).  The Postfix configuration is fairly simple, just accepts
> mail for the zbmc.eu domain and sends mail via my hosting service's
> smarthost.
>
> I want to create a similar Postfix server installation on a VPS I
> already run so that if my home desktop machine has a long down time
> for any reason I can forward my mail from my hosting provider to the
> VPS instead.  This is a simple reconfiguration on my hosting provider.
>
> The VPS has postfix version 3.3, my desktop has version 3.5.6, am I
> likely to encounter any problems with a similar main.cf on the older
> version?  I realise I have to change the myorigin, mydestination and
> myhostname but I'm hoping that's basically all.

I suggest that you look in the RELEASE_NOTES file. Configurations
that work for Postfix 3.3 should also work with Postfix 3.5.6. The
other way around is not possible if you use Postfix 3.5 features
that don't exist in Postfix 3.3.

Why can't both servers run the same version?

        Wietse

[Viktor Dukhovni]

On Thu, Jan 21, 2021 at 09:15:01PM +0000, Chris Green wrote:

> The VPS has postfix version 3.3, my desktop has version 3.5.6, am I
> likely to encounter any problems with a similar main.cf on the older
> version?  I realise I have to change the myorigin, mydestination and
> myhostname but I'm hoping that's basically all.

Not likely, but you can always check the release notes:

    https://github.com/vdukhovni/postfix/blob/master/postfix/RELEASE_NOTES-3.4
    https://github.com/vdukhovni/postfix/blob/master/postfix/RELEASE_NOTES-3.5

to see what changes were introduced between the two releases, and
whether you've managed to create a bleeding-edge configuration
that relies on Postfix 3.4 or 3.5 features.

An average user is unlikely to have any issues going back to Postfix 3.0
or even 2.10, except perhaps when using DANE, which requires 2.11, or
SNI support which requires 3.4 (or 3.5).

You can always check the postconf(5) manpage for 3.3:

    $ url="https://raw.githubusercontent.com/vdukhovni/postfix/postfix-3.3/postfix/man/man5/postconf.5"
    $ curl -sLo - "$url" | nroff -mandoc | less -R

to see whether any of the settings you're using are undocumented or
documented to behave differently (very unusual with Postfix) in 3.3.

--
    Viktor.

[Chris Green-11]

On Thu, Jan 21, 2021 at 04:33:07PM -0500, Wietse Venema wrote:

> Chris Green:
> > I currently have mail for [hidden email] and [hidden email] forwarded
> > by my hosting service to a Postfix server on my desktop machine (which
> > is zbmc.eu).  The Postfix configuration is fairly simple, just accepts
> > mail for the zbmc.eu domain and sends mail via my hosting service's
> > smarthost.
> >
> > I want to create a similar Postfix server installation on a VPS I
> > already run so that if my home desktop machine has a long down time
> > for any reason I can forward my mail from my hosting provider to the
> > VPS instead.  This is a simple reconfiguration on my hosting provider.
> >
> > The VPS has postfix version 3.3, my desktop has version 3.5.6, am I
> > likely to encounter any problems with a similar main.cf on the older
> > version?  I realise I have to change the myorigin, mydestination and
> > myhostname but I'm hoping that's basically all.
>
> I suggest that you look in the RELEASE_NOTES file. Configurations
> that work for Postfix 3.3 should also work with Postfix 3.5.6. The
> other way around is not possible if you use Postfix 3.5 features
> that don't exist in Postfix 3.3.
>
> Why can't both servers run the same version?
>

The versions of Postfix are those that are provided by the Ubuntu
repositories for the Ubuntu versions being run.  The VPS is running an
older version of Ubuntu as that's all the hosting service provides.

I *could* maybe try and install a newer version of Postfix, it's easy
enough to try I guess.

--
Chris Green