Unbelievable..... just received 30 emails that I already have received !

[#1]

Just received 30 emails that I have already received, dating back to 25/04/2012 
what is going on?

[#2]

You have your POP3 client set to leave the emails on the server and it forgot which emails it had already downloaded. Sometimes happens if a glitch occurs in the middle of downloading emails and it doesn't complete correctly, it will then download them all again.

[#3]

No, I haven`t......   BUT..... this is a "random selection" of emails... not every single one, that I have received since the date....