We are using ListServ 15.5 and are relaying out to a group of 5 smtp server at our enterprise level. The logs on these servers are filled with: 09-13-2010.00:10:04 SMTPserver-522: 1963484 host connection threshold exceeded for xxx.xxx.xxxxx.xx.xx 09-13-2010.00:10:04 SMTPserver-522: 1963485 host connection threshold exceeded for xxx.xxx.xxxxx.xx.xx 09-13-2010.00:10:05 SMTPserver-522: 1963486 host connection threshold exceeded for xxx.xxx.xxxxx.xx.xx the logs on our side look like: 14 Jun 2010 09:26:08 <421 Service not available, closing transmission channel like 400,000 times a day. The Listserv logs look normal. All the list are working fine. Has anyone run into this before? Thanks in advance, Rick