The feature currently supports IMAP only (POP3 is NOT supported). IT PAM polls the IMAP server at the port you configure in the "Mail Trigger Properties" (see the screen capture) for any new email at a polling interval defined as "Frequency".
IT PAM uses the username and password provided in the configuration. Depending on how your mail server is configured you might need to put in full email address as username (example: email@example.com instead of itpamadmin). You would normally create a new email account for this automation purpose.
IT PAM will trigger the default processes defined under "Default Process Handler" for any new email that it finds since the last time polling interval. You can only define one default process per Orchestrator. Every new default process that is created, a process variable will be populated with information from the triggering email, like subject, message body, and so forth. You can use that information in your default process to decide any further action to be taken.
The SMTP ports (see the screen capture) are for outbound emails and are not much use here in triggers.
Enabling IMAP service on the mail server is a prerequisite for this to work. If there are some restrictions on having this enabled on your corporate mail server, you will need to create sort of a "proxy" mail server. Then configure it to forward the emails from your corporate mail to this proxy mail server, which has IMAP enabled and which IT PAM can poll.
Note: The option "Use a secure SMTP connection" is also used by the IMAP mail server, in case that it is required to use a secure connection, like office365 ensure to select the check mark of this option.