PMTA (PowerMTA) – Power Mail Transfer Agent. This is a professional solution for organizing a mail server. Mailing software can be conditionally divided into two groups – PowerMTA (high-quality commercial software used by market leaders) and everything else (free Postfix, Exim, Sendmail, and others). PowerMTA is the best email deliverability solution available today.
It is used by leading Western services that send out billions of emails every month, such as Mailchimp, Silverpop, ExactTarget, iContact, Teneo, and others. GetResponse, which serves 350,000 customers, recently switched to PowerMTA.
You can also download PMTA and test the older version on your own server right now, then see how it works by yourself. (To use all features of PMTA, we recommend that you purchase a license and get a newer version of this software).
But keep in mind that the PMTA itself is just a script for sending mail. Many users mistakenly believe that by simply installing PowerMTA, they will immediately be able to send hundreds of thousands of emails without any problems. This opinion is wrong. Nothing will work without the correct configuration for each email provider.
The most serious mistake is an attempt to send mass messages immediately after installing PMTA. Before mailing (if it’s mass), you need to test the configuration first.
How PMTA actually works
The task of a PMTA is to manage the mailing processes through the dedicated IPs of the server on which it is installed. Each dedicated IP can be part of a so called vMTA (Virtual Mail Transfer Agent) which is able to work independently of other vMTAs and their results.
So if there is more than one IP on the server (or better several dozens or hundreds) PowerMTA will be able to send mail from each IP as a separate SMTP server or as part of some single vMTA with rotation (alternate replacing) of connected IPs.
If there are no problems with the mailing, they are sent according to Normal mode rules (directives). If there is a comeback due to spam (for example), PMTA sets the mailing to Backoff mode and works according to the rules of that mode. This process allows PMTA to automatically stop sending to a separate mailer, thus avoiding flooding the IP and domain with multiple Soft Bounce bounces.