Hey,
For some unknown reason, my Mail app on my Mac just gave me an error when I logged on saying "Password could not be sent to mcmasterimap.mcmaster .ca securely: Mail cannot send your password securely to the server. You can continue without a secured password, which could put your password at risk. Do you want to continue without a secured password"
I'm in my hometown, using my home Wifi, so security isn't as big an issue as it would be if I was on campus or something. Should I just ignore this or what? I didn't even do anything that would change any settings or anything.

Seems this is a common issue https://discussions.apple.com /message/12413944, http://forums.macrumors.com/showthread.php?t=1740 626, etc

Essentially you're not connecting via SSH (a secure connection) so if there were someone snooping on your home wifi using various 'hacker' tools at the time when you log into your mail app, your password would be unencrypted and visible to them while the app logs in.

One user posted a solution that you could try:

Find the 'Automatically detect and maintain' switch and turn it off on the incoming server page. THAT FIXED IT! YAY!