IMAP and "subscribing"

[Aidan Gauland]

Hello,

 As my father has already said, we've just switched ISPs.  Now I'm using IMAP 
so I don't have to download all of my E-mails (now I only have to download the 
headers of messages in threads that I don't read, instead of everything), but 
I now need to make folders on the server for sorting my mail as before (with 
POP); when I was looking at my mailboxes through the webmail interface, I came 
across an option for each mailbox called "subscribe".  This one of the many 
things for which Google is useless.  What does this option do?  There's also 
the same option in Thunderbird (my mail reader).

 Or, if anyone knows off the top of their head how to sort E-mail into 
separate folders using Thunderbird, then just tell me that.

Thanks,
Aidan