Ok real issue here. Have email domain at BT email then POP'd to exchange on 2008 sbs using the pop3 connector. Email working ok apart from a few companies. So 1st test. Emailed user to reply and it comes through ok. Test 2 - user creates new email no attachment it came through ok. Test 3 - email generated via sage with PDF attachment reaches BT server and can be viewed using BT Outlook.com web mail but when the pop 3 connector connects it disappears. Never reaches exchange. Ran message tracking on the server and there is no sign of the email. Any ideas... Have switch off AV but made no difference.