Simulate a black hole for a domain with Postfix

Introduction

When you manage outgoing emails through SMTP, you may sometimes need to test if a service is able to send correctly emails and itself check that there were no issue during sending. You can create a black hole for a specific domain and Postfix will answer from the same manner as if it is ok. It also permits to test Postfix sending capacities on a server.

Installation

Of course you need Postfix:

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aptitude install postfix

Configuration

In the Postfix main configuration, add transport map line (/etc/postfix/main.cf):

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[...]
transport_maps = dbm:/etc/postfix/blackhole_map
[...]

Now add the fake domain to the transport map file (/etc/postfix/blackhole_map):

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blackhole.com     discard:silently

Let's generate the map now:

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postmap -c /etc/postfix /etc/postfix/blackhole_map

Now restart postfix and you will see in your logs something like this:

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postfix/discard[1435]: [ID 897546 mail.info] 4D847A5B: to=<john@blackhole.com>, relay=none, delay=13, delays=13/0/0/0, dsn=2.0.0, status=sent (silently)

References

http://www.memoire-partagee.fr/2011/01/smtp-sortant-faire-un-trou-noir-avec-postfix/