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Exchange mail fails on BDAT
This is my site Written by Grant on May 18, 2012 – 11:10 pm

I had a customer exhibiting weird issues with mail between two of their company mail servers, but only in one direction  – their SBS 2003 server in Brisbane randomly failed sending email with attachments to their Exchange 2010 in Melbourne. The servers are in different domains (totally different companies) .  I happened to be remoted in late on a Friday night and noticed one email stuck in the sending queu and decided to take a look at the SMTP log files — the last line of each failed SMTP transaction for this particular email mentioned “BDAT” – something I had not seen before in SMTP logs.

On doing some research it appears that BDAT is part  of ESMTP and is involved in sending Binary DATA – apparently these advanced options can cause some issues and some people have disabled ESMTP to turn off these features.  I did some more research and found out you can disable the two main “BDAT” features while still allowing ESMTP to run.

This operation is done using Exchange PowerSHell on the receiving server.  First telnet into the SMTP server on port 25 an send the ehlo command – this shows the features currently exposed:

250-EXCHANGE1.xxxxxxxxx.local Hello [::1]
250-SIZE
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-BINARYMIME
250-STARTTLS
250-X-ANONYMOUSTLS
250-CHUNKING
250-AUTH NTLM
250-X-EXPS GSSAPI NTLM
250-8BITMIME
250-XEXCH50
250-XRDST
250 XSHADOW

 

Take note of your Server’s main ReceiveConnector name, and issue these Exchange Power Shell commands in the exact order listed::

Set-ReceiveConnector -Identity "Default EXCHANGE1" -BinaryMimeEnabled $False
Set-ReceiveConnector -Identity "Default EXCHANGE1" -Chunking $False

Now issue the ehlo command to the SMTP engine aghain and noticer that Chunking and BInaryMime are no longer listed. THis effectlively disabled the BDAT functions.

250-EXCHANGE1.xxxxxxxxx.local Hello [::1]
250-SIZE
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-STARTTLS
250-X-ANONYMOUSTLS
250-AUTH NTLM
250-X-EXPS GSSAPI NTLM
250-8BITMIME
250-XEXCH50
250-XRDST
250 XSHADOW

 

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2 Responses »

  1. I’ve seen this problem for ages. I’ve also found that it only happens between exchange servers and only if they are behind a real firewall (not just a NAT Router). I finally got WatchGuard to spend some time with me and was told to disable BDAT in their firewalls and that if I could find the commands, to disable it in Exchange.

    Just thought you might want an update on this – it’s been a problem for years, even today (3/2014).

  2. Glad it was not just me Mark! Strange how these very subtle issues can affect one or two client installations but not dozens of others — I have not seen it since myself.

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