Local only postfix for testing.

Chad Granum
September 9, 2008

Today Jonathan asked me about configuring his system to pretend to be an email server.
The goals of this task were:

  • Software under development would be able to use the local mail utilities, or use localhost as an smtp without any modifications
  • Email sent via these programs would all be delivered to a static location instead of the destination address, to be read at another time
  • No email would be relayed out to spam anyone else.

I have configured local email for development in the past, which is why Jonathan came to me with this. Immediately I decided to use postfix because it is easy to configure and use. Initially I looked at address masquerading or rewriting, but these solutions were overcomplicated and did not appear to solve all the problems.

Eventually I found a site explaining how to disable local delivery (the opposite of what we needed). The way to disable the local delivery was to comment out the 'local' configuration option in /etc/postfix/master.cf. Looking at the file it was clear that it mapped source to destination.

smtp      unix  -       -       -       -       -       smtp
relay     unix  -       -       -       -       -       smtp
local     unix  -       n       n       -       -       local

The idea was simple, map 'smtp' and 'relay' to 'local'
smtp      unix  -       -       -       -       -       local
relay     unix  -       -       -       -       -       local
local     unix  -       n       n       -       -       local

The results were exactly as desired. No email is delivered to the outside world, and all email is placed in /var/spool/postfix/active. According to Jonathan, his applications run seamlessly, completely unaware of this.

Tagged as: mail, master.cf, postfix, sandbox, smtp, testing

3 comments

Dylan Tack wrote 3 years 9 weeks ago

Delivery to a local mailbox

This is a very useful setup, thanks. I found that messages were formatted a bit inconveniently when sitting in the Postfix active spool. By adding a virtual alias map, I was able to get Postfix to deliver them to a local mailbox (/var/mail/djtack, for me), where they can be read with a normal MUA (I'm using Pine currently).

# add to /etc/postfix/virtual, then run `postmap /etc/postfix/virtual`
/.*/ djtack@localhost
 
# add to main.cf
virtual_alias_maps = regexp:/etc/postfix/virtual

Ignatius Teo (not verified) wrote 1 year 39 weeks ago

Forward locally delivered mail to another Postfix instance?

Hi guys,

This was extremely helpful and easy to follow. But here's my scenario. I am running a Turnkey Linux LAMP stack in a VirtualBox VM, bridged on a static IP of 192.168.1.3. I have setup postfix on the VM as above, and I can get all mail delivered to /var/mail/ignatius. Problem is I can't get to this using Thunderbird's Movemail account.

I also have postfix installed locally on my host desktop as well (hostname is ignatius-desktop). Question: How do I forward locally delivered mail on the VM to the host?

Or is there a simpler option?

Alex S. (not verified) wrote 1 year 22 weeks ago

Brilliant!

Thank you, worked like a charm!