Incoming maiflow Stuck. Share on Facebook Post on reddit Tweet on Twitter Share on LinkedIn Home › Forums › Messaging Software › Exchange 2007 / 2010 / 2013 › Incoming maiflow Stuck. This topic has 3 replies, 4 voices, and was last updated 12 years, 11 months ago by Elan Shudnow. Viewing 1 post (of 1 total) Author Posts aatishMember Oct 12, 2007 at 3:03 am #128233 Incoming maiflow Stuck. When we try to telnet hub transort on 25 port following error gives: 421 4.3.2 Service not available, closing transmission channel HUB is refusing all incomming mails ……. What are the possible causes for same. Author Posts Viewing 1 post (of 1 total) You must be logged in to reply to this topic.