Exchange 2010 - 550 unknown user

[Zoom7000]

I've just been given a handover of the Exchange 2010 system at a Charity Girls' School that I am now responsible for. I have tried to create a new email account for myself and a new member of staff, however, none of the new accounts can receive emails from external. We can send emails, but when receiving the sender gets a bounce back:

 

Delivery to the following recipient failed permanently:

 

[username]@quwwatulislam.com

 

Technical details of permanent failure:

Google tried to deliver your message, but it was rejected by the server for the recipient domain quwwatulislam.com by mail.quwwatulislam.com. [79.170.40.19].

 

The error that the other server returned was:

550 unknown user

 

What's also interesting is last night I tried to edit the email address policy. Staff have been complaining that they have horribly complex usernames and the email addresses are in the format of [email protected]. They would prefer having [email protected].

 

So, I went in to the policy which was currently set as %[email protected] and I added %g.%[email protected] and set it as the reply to primary SMTP address. However, this morning all external emails were being bounced back with the 550 unknown user error. I have set the %[email protected] back as the default and all is working again. However, the firstname.surname alias won't work for any existing users and the 2 new accounts I have created cannot receive emails at all even with [email protected].

 

Any ideas?

[Norphy]

Are they using a service like Mimecast to do their spam filtering? It could be that you need to sync a list of allowed email addresses with this hypothetical provider and that this isn't happening.

[Zoom7000]

Are they using a service like Mimecast to do their spam filtering? It could be that you need to sync a list of allowed email addresses with this hypothetical provider and that this isn't happening.

 

No, they are using AVG anti spam, but I can't see any settings that would be blocking the emails.

 

Just for the record a lot of Google searches are saying check that the Require that all senders are authenticated is disabled. I have checked this and it is disabled.

[Norphy]

Are your emails coming straight to you or are they being forwarded from another SMTP server such as one from your LA? As I'm sure you know, you can find this out by looking at your domain's MX record.

[Roberto]

Hmm...

 

It looks like you have a smarthost. (extendcp.co.uk?) in front of your exchange server. I suspect that, as norphy says, they are not relaying outgoing email for SMTP addresses they are unaware of, which is good practice really.

 

Connecting to 79.170.40.19

 

220 mail44.extendcp.co.uk ESMTP Exim Thu, 27 Mar 2014 13:04:12 +0000 [975 ms]

EHLO smtp.mvps.org

250-mail44.extendcp.co.uk Hello mail.mvps.org [216.155.126.34]

250-SIZE 31457280

250-8BITMIME

250-PIPELINING

250-AUTH PLAIN LOGIN CRAM-MD5

250-STARTTLS

250 HELP [718 ms]

MAIL FROM:

250 OK [719 ms]

RCPT TO:

550 relay not permitted [736 ms]

[Zoom7000]

The registrar for the domain is 123reg. Unfortunately the previous guy still hasn't transferred ownership of the domain in to my name. Would 123reg be the one controlling the relay?

[Norphy]

It doesn't look like it. That IP seems to be registered to a Heart Internet Ltd.

 

Is your Exchange instance on site or hosted?

[Zoom7000]

It's on site.