A MTA or Mail Transport Agent is a software application that is used to transfer email messages between computers or servers.
MTAs play a crucial role in the email infrastructure, and they are responsible for delivering email messages from one server to another.
There are several popular MTAs available, such as Postfix, Sendmail, and Exim.
Your PC or mobile phone also uses an MTA to send emails, an outgoing mail server, which it connects to via the SMTP protocol and authorizes with a user name and password.
Software running on the same server as the MTA can bypass authorization and queue an email directly to the MTA. This uses, for example, the PHP function mail(), on which the WordPress function wp_mail() is based.
The MTA works by receiving incoming email messages and forwarding them to the appropriate email server. When an email message is sent to a domain, the MTA looks up the mail exchange (MX) records for that domain in DNS to determine where the email should be delivered. It then delivers the email to the designated email server.
Using a MTA from within WordPress
WordPress has built-in email functionality that allows you to send email notifications to your users. As previously mentioned, the standard WordPress wp_mail() function also uses the server’s MTA by sending outgoing emails to its outbox queue.
The big problem is that a web server on which WordPress is running usually is not configured perfectly to send emails. In consequence emails from this server mostly end up in the recipient’s spam folder.
For this reason, many WordPress webmasters use a plugin that does not route all outgoing WordPress emails through the server’s MTA, but a correctly set up (external) SMTP mail server. However, this significantly reduces the throughput of emails, because communication with an SMTP server takes about one second per email. The SMTP service can also result in high costs.
Our WordPress plugin Campation Post Office™ solves this problem for every WordPress webmaster by professionalizing the use of the MTA from within WordPress. Starting with an assistant that supports the WordPress webmaster in correctly configuring his domain in the DNS, to its proprietary, MTA-based sending technology Campation SpeedMail™, as well as your automatically connected dedicated IPv6 mail server Campation DediMail™ which can even send emails in parallel (simultaneously), this plugin solves the WordPress email problem in a very elegant, sophisticated way!