SBS 2011 Standard (Exchange 2010) 554 5.1.0 Sender Denied

Had a puzzler last week. Client called up to say one of his contacts couldn’t email him. It was being rejected.

Message Rejections will be a common problem for many people, and the best thing to do is get a copy of the rejection message or what i call NDR (Non Delivery Receipt (or Report) )

Luckily in this case, there was actually an NDR generated, because some times email can just seem to vanish into the ether, and you’re left with little to go on…

Also luckily for me the third party was happy to send on the NDR via my client’s secretary.

The smart ones reading will now have figured out that the rejections were only to my caller – the third party was able to email the secretary successfully.

Here is the NDR

NDR Message

You can see that the Error Code is #5.1.0 smtp; 554 5.1.0 Sender denied

Sender denied i thought… sounds like something was configured in Exchange… which it turns out it was, but not what i thought.

Also, the NDR in question was generated by their Exchange server, not by their Offsite AntiSpam service, which helped me quickly identify that the issue was at their Exchange, not at the Anti Spam service.

Sender Filtering, is one of the Anti Spam tools enabled and running by default on SBS 2011 Standard.

Usually the NDR above would be associated with an address that is blocked by the Sender Filter running on the Hub Transport Role.

However in this case there were no addresses blocked by the Sender Filter at the server level.

(if you want to look at the Anti Spam tools, i have covered their location at the end of the post)

In this case the address was defined by the users own Junk Mail settings.

I logged into the SBS RWA (Remote Web App) and logged into Outlook Web App (OWA)

SBS RWA

Clicking on to Options, then More Options, there is a ‘Block or Allow’ option in the menu on the left hand side.

Outlook Web App

Outlook Web App Options

OWA Options

If you click here you can see a list of Allowed Senders, and a list of Blocked Senders.  Scroll Down to see Blocked Senders.

OWA Block or Allow

OWA Blocked Senders

Sure enough the email address being rejected was set to be blocked. Removing the address from this list will allow emails to be received from that address. Make sure to save the changes and that should solve the problem.

Remove Blocked Sender

It wont solve the mystery of how the address ended up as a blocked sender, but that mystery will live on, like the other great mysteries we face, such as using a PC during a power cut, Photocopying a floppy disk to use as a backup, and using the optical drive as a beverage cup holder.