https://community.spiceworks.com/topic/1694735-message-rejected-by-server-exchange-2010-and-ipad
Please see solution below
I get that, but its not 10mb its 7.9mb
its like ActiveSync is saying you can only send 6mb not 10mb
Thank you Da_Schmoo, I did a google search and found that if I change the web.config file in this location on the server: C:\Program Files\Microsoft\Exchange Server\V14\ClientAccess\Sync
then opened up the web.config file in notepad and scrolled down till I saw <httpRuntime maxRequestLength=”10240?/> was set to 10 MB.
I have changed it to 25600(25 MB) for resolving the issue.
Found on Spiceworks: https://community.spiceworks.com/topic/1694735-message-rejected-by-server-exchange-2010-and-ipad?utm_source=copy_paste&utm_campaign=growth