Different IP for Email

I want to put one domain on a separate IP address for email. When I create an email box, I don't see any place to enter an IP. How is this done?

 

Thanks, Till. How can I change the IP address for mail only--on the whole server? Or is this a bad idea? I've been using an IP address for mail for a long time, and I'm wondering if it's time to change.

 

Postfix does support this, we have a single server (debian wheezy, non-ispconfig) using separate ip addrs for a couple domains (incoming and outgoing).

The outgoing piece uses sender_dependent_default_transport_maps to select the default transport according to the sender address, eg. set this in main.cf

Code:

sender_dependent_default_transport_maps = texthash:/etc/postfix/sender_dependent_default_transport_maps

then create /etc/postfix/sender_dependent_default_transport_maps with:

Code:

@dom1.com  dom1_smtp
@dom2.com  dom2_smtp
DUNNO

Then you create dom1_smtp and dom2_smtp transports that specify a different smtp_bind_address option, eg. in master.cf:

Code:

dom1_smtp      unix  -       -       -       -       -       smtp
    -o smtp_bind_address=x.x.x.x

dom2_smtp      unix  -       -       -       -       -       smtp
    -o smtp_bind_address=y.y.y.y

The incoming pieces are handled similarly, ie. multiple transports created to listen on each address and set a few options differently.

For another option, I believe you can accomplish the same thing with postfix instances as well, but I don't have a working example offhand.

 

One other thing that might be useful if someone were to incorporate such a config into ispconfig, we actually set variables with the bind IP addresses and use those in the transport definition. Eg. in main.cf:

Code:

dom1_smtp_bind_address = x.x.x.x
dom2_smtp_bind_address = y.y.y.y

And in master.cf:

Code:

dom1_smtp      unix  -       -       -       -       -       smtp
    -o smtp_bind_address=$dom1_smtp_bind_address

dom2_smtp      unix  -       -       -       -       -       smtp
    -o smtp_bind_address=$dom2_smtp_bind_address

You can then use postconf -e to set/change the ip address, rather than parsing master.cf (I don't know how how ispconfig handles that, it may or may not be easier).