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iOS 7 and sending emails larger than 40KB from Exchange accounts

Since upgrading iPhones (4, 4S and 5) to iOS 7 when sending messages that are larger than about 40KB from exchange accounts we are getting the message "Cannot Send Mail. The message was rejected by the server because it is too large."


The same phones don't have any issues sending to from other emails accounts (gmail, yahoo, etc).


We are on Exchange 2010 SP3 RU2.The Exchange server does have size restriction of 50MB.


These accounts have no issue sending the same emails through Outlook or OWA. It is strictly related iOS.

iPhone 4S, iOS 7, Exchange mail accounts

Posted on Sep 20, 2013 10:02 AM

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16 replies

Sep 23, 2013 11:12 AM in response to loucie

We are seeing intermittent issues with IOS 7 devices on Exchange with smaller messages. Cannot find a log of the message on the iPhone, but it indicated it was rejected by the server. At first it seemed to be an issue of a period at the end of the email. We were able to recreate this once, but then subsequent attempts to recreate faile and all emails were processed correctly.

Sep 23, 2013 8:14 PM in response to loucie

Update to my scenario. I figured it out. We are on Exchange 2007 on Server 2003 and we are using Active Sync with Client Certificates. We did not notice much of a problem when sending using IOS 6 but with IOS 7 it was much more prevalent, any message over 100K would get rejected as too large. turns out it was a problems with IIS 6 and the uploadreadaheadsize value in the IIS metabase. Here is a link regarding it for 2010

http://social.technet.microsoft.com/Forums/exchange/en-US/52f58b47-b95e-4f44-bb4 e-6bd8b1b4eb94/iphone-sending-attachment-problems


here is one for 2007

http://technet.microsoft.com/en-us/library/cc737382%28WS.10%29.aspx


I bumped mine up to 10Mb and now attachments are going through fine. THis probably should have been done a long time ago, but the symptoms really just reared its ugly head after the ios 7 upgrade.


I hope this helps others, as i was pulling my hair out all weekend trying to figure this out.

Sep 27, 2013 7:21 PM in response to cli1010

I would go for it. THis is the link to do it on 2008. Just look up how to back up the metabase first. Also find out how to query the current values in metabase to ensure your changes went through and or to revert back. At lease look for more information using the link below as a starting point.



http://social.technet.microsoft.com/Forums/exchange/en-US/52f58b47-b95e-4f44-bb4 e-6bd8b1b4eb94/iphone-sending-attachment-problems

Sep 28, 2013 7:02 AM in response to tsmith06117

We've had this setting in place for a few days with no issues.


Some research on the UploadReadAheadSize setting:

http://technet.microsoft.com/en-us/library/cc737382%28WS.10%29.aspx

Setting the UploadReadAheadSize property above 64KB is not recommended for web sites that do not require client certificate authentication, otherwise you run the risk of allowing an anonymous Denial of Service (DOS) attack. When UploadReadAheadSize needs to be set at a value higher than 64KB, it is recommended that you set the SSLAlwaysNegoClientCert property to True, which will require that the client has a valid client certificate installed.


SSLAlwaysNegoClientCert: http://technet.microsoft.com/en-us/library/cc778630%28WS.10%29.aspx

We are investigating the possibility of turning this on instead.



iOS 7 and sending emails larger than 40KB from Exchange accounts

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