• If there is a malformed header line the e-mail, the user doesn't get e-mail. After some time the POP3 connector stop processing the mailbox. The fix is to manually delete all messages and recreate the mailbox.
   
• The POP3 connector can't download an e-mail over 10MB even your Exchange has no limit, becuse the limit of 10MB is inside the POP3 connector.

Small Business Server SBS 2003:

• The POP3 connector can't collect faster then every 15 minutes.
   
• The POP3 connector retrieves the user's email (john.doe@domain.com) and routs it to the appropriate local Exchange mailbox (jdoe@domain.local), just like it's supposed to do, but only if jdoe@domain.local is set as the primary reply-to addresses under the Email Addresses tab in the user's properties.
   
• The POP3 connector bypasses spam and virus checkers.
   
• The POP3 connector can't handle BCC, even when the ISP adds them to the header lines.