As demonstrated in our previous recipe, NGINX can do pure TCP load balancing. Further to this, there are some protocol specific implementations, which have some specific items to enhance the implementation.
Simple Mail Transport Protocol (SMTP) is the standard protocol used to send and receive email at a server level. The most popular SMTP servers for a Linux platform include Postfix, Exim, and Sendmail, with Exchange being the most popular for Windows.
Load balancing SMTP can help to distribute the sending and receiving of email, especially if it's a high-volume environment such as an Internet Service Provider (ISP). By running multiple servers, you can distribute the sending aspect as well as provide some fault tolerance when systems have issues.
While NGINX has a specific mail module, unfortunately, this does not have load balancing capabilities...
