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Tuesday, April 30th, 2013 12:00 PM

421 4.4.2 connection dropped due to connection reset error - Only to Hotmail accounts

Had RDNS setup by Comcast support and I'm not sure if RDNS is "case sensitive" but everything appears to be correct with my DNS and Exchange server configurations but I'm still unable to send to Hotmail email addresses. The STMP log show 421 4.4.2 connection dropped due to connection reset for these message. My mail server is and the ip is

Accepted Solution



1.5K Messages

11 years ago

Hello stryder9,


Welcome to the forum.

Based on your post and we test your domain on for blacklisting. (Link)

We didn’t see any block listed on this test, so it points to possible filter issue on their server.

This is e-form from Microsoft for requesting of checking/de-listing domains that can't send to their email domains.

MSN E-Form

They will be able to check your domain for you.


Additionally please note the Microsoft’s decision to move their Hotmail users to email service.

Here some article entailing it:

Outlook Blog - MSN

Outlook Upgrade FAQ - MSN


Thank you