Repairing permissions. Could you explain.

I'm logging onto yahoo.de and web.de pop3 mails. Until a few days ago the web.de worked 100% ok. The Yahoo has been a bit 'iffy' for months. (The yahoo.de accounts work differently to the yahoo.com accounts, they are accessable from any computer).
If I wipe my accounts and re-setup, what do I have to do to protect my mail I have?
My ISP is MaroccoTelekom.