Downloading messages times out

I am starting to re-use an old e-mail address. I believe the problem is that
there are a number of old messages that have been sitting there from before.
It is too large to download them all at once and the server keeps timing out,
I even left it running all night, hoping that would solve the issue, I also
have tried changing the headers only, size of files etc. I just cannot seem
to get rid of the old ones and start fresh with the new... working address is
problem address is .
What should I do?