Hello Nicholas,
To add to what Zach mentioned above. If you are seeing an issue with messages not being received you will want to start with the POP log.
Settings -> Diagnostics -> Log Files -> {date}-POP-{#}.log
If you see that the message was imported here grab the EML number from the log.
00:23:46.439 [{server}:{user}] CMD: RETR 1
00:23:46.439 [{server}:{user}] Saved as: 388fe11610a841688f3587200fa51202.eml
00:23:46.439 [{server}:{user}] CMD: DELE 1
Next you can search the import log for this message id
Settings -> Diagnostics -> Log Files -> {date}-TicketImport-{#}.log
04:44:18.659 ==================================
04:44:18.659 Starting Ticket Import Session For 1 Messages
04:44:18.659 -------------------
04:44:18.659 Started Handling Message
04:44:18.659 Pop Department: {department}
04:44:18.659 File path\name: C:\SmarterTrack\App_Data\Spool\in-39\388fe11610a841688f3587200fa51202.eml
04:44:19.083 Ticket Saved [3D0-2A681563-0B05]
04:44:19.083 Ticket sent to agent if needed
04:44:19.083 Finished importing message
04:44:19.083 -------------------
04:44:19.083 Completed Ticket Import Session
04:44:19.083 ==================================
Here you will either see an error or nothing at all. The next place to review will be the error logs.
Settings -> Diagnostics -> Log Files -> {date}-Errors-{#}.log
Thank you
Tony Scholz
System/Network Administrator
SmarterTools Inc.
www.smartertools.com