squiggle here (I need to sort my account out).
The from line in an email isn't much of a guarantee. Basically anyone can appear to be anyone else. Viewing the message source/headers will show the path the email has taken though.
As I think Ian suggested. If you get an email purporting to be from PayPal and you are unsure. Do not follow the link. Open a browser and navigate your own way )perhaps a bookmark you have set) to the company web site. If there really is something that needs your attention, it should become apparent when you log in.
POP vs IMAP
In the first instance, which you use depends on the email server. Some but by no means all email servers do support both protocols. I'd think any email client (eg. thunderbird, outlook, etc.) will support both.
When you do have a choice, it might be worth considering a difference between the 2.
POP: While it is possible to leave a message on the server, POP was designed with the idea that you download messages from the server onto your local email program.
IMAP: on the other hand was designed with the idea of a central email storage. As such, I think it is more appropriate for our typical email usages these days where we may for example be wanting to access email from both a mobile device and our desktop computer.
