421 invalid sender domain error Share on Facebook Post on reddit Tweet on Twitter Share on LinkedIn Home › Forums › Messaging Software › Exchange 2007 / 2010 / 2013 › 421 invalid sender domain error This topic has 8 replies, 2 voices, and was last updated 11 years ago by bigalusn. Viewing 1 post (of 1 total) Author Posts bigalusnMember Aug 04, 2009 at 12:16 pm #143571 Exch Server 2007, on Windows 2003 Standard Ed. DC’s are Windows 2003 Standard Ed as well. In Exchange, under Queue Viewer I get the following error while trying to send to some outside domains. All other domains receive mail from our domain just fine. Error: Identity: BMP-EXCH3752162312894 Subject: RE: Lambda Problems Internet Message ID: < [email protected]om> From Address: firstname.lastname@example.org Status: Ready Size (KB): 20 Message Source Name: FromLocal Source IP: 255.255.255.255 SCL: -1 Date Received: 8/4/2009 9:00:58 AM Expiration Time: 8/6/2009 9:00:58 AM Last Error: 421 invalid sender domain ‘metrohmusa.com’ (misconfigured dns?) Queue ID: BMP-EXCH375216 Recipients: [email protected] Author Posts Viewing 1 post (of 1 total) You must be logged in to reply to this topic.