Create a fake mail server to test mail functions in applications

Written by - 0 comments

Published on - Listed in Linux Mail

Developing and testing applications sometimes require you to go the "non-standard" way. A good example is when you have a web-application which has a mail function. The mails must correctly be sent but remember, this is just a test of the application and you don't want your users to get spammed with test mails. 

A fake/dummy mail server comes in handy. A developer suggested MailCatcher, which looked good to me except that it's written in ruby and depends on gems which I didn't want to put on this system. At least not if I find something easier...

Then I came across Dummy-SMTP, a simple listener written in python (so no additional software to be installed on my Ubuntu test servers) just saving all the received mails as text files in a folder.
By default, Dummy-SMTP runs on port 25 which requires root privileges to start with and it also must be started from within the correct folder. I made some modifications for the following purposes:

  • Launch the listener as non-root user
  • Launch the listener from anywhere with the absolute path

In my case, I defined the listener port to be 1025 and defined an absolute path: /srv/Dummy-SMTP which I chose where to run the listener.
To install Dummy-SMTP either clone the original repository or my forked one:

cd /srv/
git clone
chown -R appuser:appuser /srv/Dummy-SMTP

 Once the repository was cloned, become "appuser" if you aren't already and launch the file:

appuser@app01-test:~$ /srv/Dummy-SMTP/ &
[1] 32189
Running fake smtp server on port 1025

Now I adapted the Postfix installation and defined that all mails should be relayed to this fake smtp server by setting the relayhost parameter:

cat /etc/postfix/|grep relayhost
relayhost =

service postfix reload

From now on a mail sent from this server should be relayed to the dummy smtp server and be just stored as a text file in /srv/Dummy-SMTP/mails. Let's try this:

echo "Dummy SMTP Test" | mailx -s "Test"

mail.log shows:

app01-test postfix/pickup[30289]: 3559024A6A: uid=0 from=
app01-test postfix/cleanup[4940]: 3559024A6A: message-id=<20160607120336.3559024A6A@app01-test.local>
app01-test postfix/qmgr[30290]: 3559024A6A: from=, size=385, nrcpt=1 (queue active)
app01-test postfix/smtp[4942]: 3559024A6A: to=, relay=[]:1025, delay=0.03, delays=0.02/0.01/0/0, dsn=2.0.0, status=sent (250 Ok)
app01-test postfix/qmgr[30290]: 3559024A6A: removed

And let's check out the Dummy SMTP mail folder:

ls /srv/Dummy-SMTP/mails

cat /srv/Dummy-SMTP/mails/1465301016.24.txt
Received: by app01-test.local (Postfix, from userid 0)
    id 3559024A6A; Tue,  7 Jun 2016 14:03:36 +0200 (CEST)
Subject: Test
X-Mailer: mail (GNU Mailutils 2.99.98)
Message-Id: <20160607120336.3559024A6A@n
Date: Tue,  7 Jun 2016 14:03:36 +0200 (CEST)
From: root@nzzshop-app01-test (root)

Dummy SMTP Test

Neat! It worked.

The above mentioned Ruby alternative Mailcatcher has one nice feature though: The mails can be seen by browser. Well, this isn't very complicated either. The mail folder of the dummy smtp server is a given (/srv/Dummy-SMTP/mails) so by creating a simple "Alias" on the Apache running already on this test server, I was able to display all sent mails on the browser, too:

cat /etc/apache2/conf-enabled/dummysmtp.conf
Alias /mails "/srv/Dummy-SMTP/mails/"

<directory /srv/Dummy-SMTP/mails>
    Require all granted
    Options +FollowSymLinks +Indexes
    AllowOverride All

service apache2 reload

Nothing fancy of course, but it works:

Fake dummy smtp server showing mails in browser

Add a comment

Show form to leave a comment

Comments (newest first)

No comments yet.

RSS feed

Blog Tags:

  AWS   Android   Ansible   Apache   Apple   Atlassian   BSD   Backup   Bash   Bluecoat   CMS   Chef   Cloud   Coding   Consul   Containers   CouchDB   DB   DNS   Database   Databases   Docker   ELK   Elasticsearch   Filebeat   FreeBSD   Galera   Git   GlusterFS   Grafana   Graphics   HAProxy   HTML   Hacks   Hardware   Icinga   Influx   Internet   Java   KVM   Kibana   Kodi   Kubernetes   LVM   LXC   Linux   Logstash   Mac   Macintosh   Mail   MariaDB   Minio   MongoDB   Monitoring   Multimedia   MySQL   NFS   Nagios   Network   Nginx   OSSEC   OTRS   Office   PGSQL   PHP   Perl   Personal   PostgreSQL   Postgres   PowerDNS   Proxmox   Proxy   Python   Rancher   Rant   Redis   Roundcube   SSL   Samba   Seafile   Security   Shell   SmartOS   Solaris   Surveillance   Systemd   TLS   Tomcat   Ubuntu   Unix   VMWare   VMware   Varnish   Virtualization   Windows   Wireless   Wordpress   Wyse   ZFS   Zoneminder