Email being rejected on some email addresses

itwarlord
itwarlord used Ask the Experts™
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SBS 2011, exhchange 2010, single server environment.  Suddenly yesterday, several users stopped getting email on some of their alternate email addresses.  each employee has FI.lastname@domain.com and FIlastname@domain.com.  they will receive one email but the other is returned 550 5.1.1 user unknown.
Unfortunately, we do have a higher headquarters that receives all our email, but they say it is not their item.

If I telnet from the exchange server, I get both email addresses to show up.

If they come from the outside, routed through the parent company, only one gets through.
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what email gateway you are using..?

it could probably happen if you sync your identities to the mail gateway and block email receive for sender which does not exist, what you can check is if the recipients who have this issue, if their all the proxy address are synced?
itwarlordSenior Engineer/Owner

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Commented:
I will ask.  thanks
Senior Engineer/Owner
Commented:
Higher headquarters found an authentication error.

problem solved.

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