As you may know, the Exchange Online ActiveSync Protocol and configuration is set to limit messages attachments to 10MB or less. When sending an attachment that is close to 10MB, you will need to look at compressing/zipping the file to a smaller size before the EXO ActiveSync protocol will allow the message to be delivered. When using an ActiveSync device, such as a mobile phone, iOS (iPad, iPhone, etc) device, it may be difficult to get the attachment zipped and then sent, but at this time this is the only way in which you can work within the ~10MB ActiveSync configuration setting.
- Save the file to your desktop
- Zip/Compress the file to decrease the size of the file, the more compression the better to make sure you don’t hit this 10MB attachment limit
- Connect your ActiveSync device and bring the file back into the device or send mail, attaching the compressed attachment