When sending from a Mobile device via the ActiveSync service the device fails to send.
Some devices may return an error indicating that "The message that was sent to the server was rejected because the message was too large". (Apple iPad iOS 7). Not all mobile devices behave this way and may just keep the message in the outbox folder and retried until removed from the folder.
A global IIS restriction preventing uploads larger than 49152 Bytes.
IIS 7.5 sets a default value of 49152 Bytes for the "UploadReadAheadSize" value which limits the amount of bytes allowed in the entity body of a request and the number of bytes a Web server will read into a buffer and pass to an ISAPI extension.
2013-11-27 23:43:48 192.168.0.1 POST /Microsoft-Server-ActiveSync Useremail@example.com&DeviceId=ApplDMRL2W3PF185&DeviceType=iPad&Cmd=SmartForward 443 - 192.168.0.2 Apple-iPad3C4/1102.55400001 413 0 0 6396
2013-11-27 23:43:48 192.168.0.1 POST /Microsoft-Server-ActiveSync Userfirstname.lastname@example.org&DeviceId=ApplDMRL2W3PF185&DeviceType=iPad&Cmd=SendMail 443 - 1918.104.22.168 Apple-iPad3C4/1102.55400001 413 0 0 6396
The above log snippets report a 413 error in the line which indicates the "Request Entity is too large".
Where "14" in the above command is the website ID
|Product:||MailEnable (ME-6.X Pro-Any Ent-Any)|
|Keywords:||send Activesync UploadReadAheadSize large size attachments attachment|
|Class:||TRB: Troubleshooting (Configuration or Environment)|
|Revised:||Wednesday, May 4, 2016|