Problems using Outlook to collect emails

Hi,

I am having some problems that have been going on for a few weeks.
When using Mailwasher, the headers are downloaded fine, but when I then load up Outlook 2003 to retrieve my emails, it often times out retrieving from the domains on the site.
It's usually just 1 domain it has problems with (a domain which has been on the system a while). I have to keep checking the mail until it goes through.

Any reason for this?

James