When comparing MailerQ vs Postfix, the Slant community recommends Postfix for most people. In the question“What are the best Linux mail transfer agents (MTAs)?” Postfix is ranked 2nd while MailerQ is ranked 5th. The most important reason people chose Postfix is:
Almost all Sendmail milters can be used with Postfix out of the box.
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Pros
Pro Fast and reliable
Only MTA out there built on RabbitMQ, a message queeing broker, which means that no messages are stored on the disk, increasing the performance speed of your deliveries as well as reducing unnecessary hardware costs. Setting up in a cluster, both RabbitMQ and MTA will make sure that in case of a server fail, the messages are continued to be delivered and the other cluster picks up the slack.
Pro Scalable and highly controllable
This product is highly scalable and configurable to your exact requirements. With a friendly Management Console, you can adjust and set all the settings on the go as well as control and oversee your campaigns and clients. The MailerQ keeps building new features which means that customer needs and requirements are taken in consideration to add valuable and good features.
Pro Can run sendmail milters
Almost all Sendmail milters can be used with Postfix out of the box.
Pro Resource efficient and fast
Due to its modular design, Postfix can be configured to only use parts that are required in each use-case and as such conserves resources and operates fast.
Pro Good documentation
Postifx has a thorough documentation with examples.
Pro Active development
New releases are typically 2-3 months apart.
Pro Flexible and easy to administer
Postfix uses a monolithic, flexible, human-readable configuration file with sane defaults and since it's modular, each module can be used, ignored or switched with another depending on needs.
Pro Security focused
Postfix was built ground up with security in mind. It is highly secure. As such it can at times be a bit less flexible than Exim.
Pro Sendmail compatible
Postfix is a drop-in replacement for Sendmail. It implements a compatibility interface with some options silently ignored.
Cons
Con No official version-controlled repository
See discussion at https://groups.google.com/forum/#!topic/mailing.postfix.users/6Kkel3J_nv4 and unofficial repo at https://github.com/vdukhovni/postfix
Con Pain in the neck to configure
Postfix is hard to configure: be prepared to spend some time configuring TLS and permissions, through trial and error. Postfix is an awesome MTA but if you are looking for a quick and functional setup, don't use it.