After upgrading to 2.1.1 I cannot seem to send to my list anymore. The stmp-failure log is full of

Feb 25 21:32:35 2003 (95755) delivery to xxxxxxxx@pics.com failed with code 553: 5.1.3 <pics-mail-bounces+xxxxx=pics.com@>... Hostname required Feb 25 21:32:35 2003 (95755) delivery to tttttt@pics.com failed with code 553: 5. 1.3 <pics-mail-bouncesttttt=pics.com@>... Hostname required

Any help would be most appreciated.

Thanks

Terry