new user to IMAP vs POP3

[#1]

I have just been playing with IMAP - nearly successful but don't seem able to get at the properties tab until I open the mail,  with POP3 I can look at the properties and then headings, also raw e-mail without any risk of virus etc.
Why is properties greyed out?

[#2]

Because with IMAP, the email remains on the PlusNet servers - all you are doing is viewing the basic info (from/to/subject/date etc). Only when you click to view it does it download (a copy) of the email to your local PC when you can then look at the properties.
The is the main difference between IMAP and POP3. With POP3, when you see the email in your inbox, it has already been downloaded and deleted from the mail server. With IMAP you just see the basic info and only download a copy of it when you click to view it, leaving the original on the server.