I have recently migrated a client from SBS 2003 to SBS 2008. Everything has been going fine till today, now external email can't be received. The message I get is :
email@example.com on 06/04/2009 12:00
The e-mail system was unable to deliver the message, but did not report a specific reason. Check the address and try again. If it still fails, contact your system administrator.
< mk-outbboundfilter-4.mail.uk.tiscali.com #5.0.0 smtp; 5.1.0 - Unknown address error 550-'5.7.1 Unable to relay' (delivery attempts: 0)>
Can anybody help me ?