Summary
In this chapter, we saw how NGINX can be configured to proxy POP3, IMAP, and SMTP connections. Each protocol may be configured separately, announcing support for various capabilities in the upstream server. Encrypting e-mail traffic is possible by using TLS and providing the server with an appropriate SSL certificate.
The authentication service is fundamental to the functioning of the mail module, as no proxying can be done without it. We have detailed an example of such an authentication service, outlining the requirements of both what is expected in the request and how the response should be formed. With this as a foundation, you should be able to write an authentication service that fits your environment.
Understanding how to interpret log files is one of the most useful skills a system administrator can develop. NGINX gives fairly detailed log entries, although some may be a bit cryptic. Knowing where to place the various entries within the context of a single connection and seeing...
