Outlook Express Maximum Number of Accounts

If you have more than 32 email accounts set up in Outlook Express only 32 of them will download automatically.

The rest will have to be downloaded on individual send and receive runs.

http://support.microsoft.com/?kbid=296513
Outlook Express is designed to handle e-mail message checking for no more than 32 POP3 accounts.

One option may be to create an extra identity, and switch between the two, each time you do a email download.

File :  Identities :  Add New Identity