This article will outline the different message size limitations based on several scenarios:

  • Internal Messages: 150MB
  • Outbound to external recipients - non-encrypted messages: 75MB
  • Outbound to external recipients - encrypted messages: 30MB
  • External user initiated message to us from the Proofpoint Portal: 15MB
  • Messages sent with Outlook Mobile: 33MB


Internal Messages

When sending internally to any user within our Microsoft tenant (any end-user within one of our agencies that has a mailbox, shared mailbox or Distribution List) have a max size limit of 150MB


Outbound to external recipients - non-encrypted messages

When sending a message to an external recipient where the message is not encrypted (does not contain PHI/PII), the max size limit is 75MB

Note: The external recipient may also have a max size that they will accept


Outbound to external recipients - encrypted messages

When sending a message to an external recipient where the message contains PHI/PII and is encrypted through the following process, the max size limit is hard set by the vendor (Proofpoint) at 30MB.  This size limit cannot be adjusted

Process to send an encrypted message: https://support.patriotgis.com/support/solutions/articles/17000086342-how-to-send-a-secure-email-message

If PHI/PII needs to be sent externally, and the file is larger than 30MB, you may need to send the file through another method such as securely sharing the file through SharePoint or OneDrive: https://support.patriotgis.com/support/solutions/articles/17000012196


External user initiated message to us from the Proofpoint Portal

If an external contact is attempting to initiate a net-new message from the Proofpoint Secure Portal through the following process to be sent to an internal user, the max size limit is hard set by the vendor (Proofpoint) at 15MB.  This size limit cannot be adjusted.

Process for an external user to initiate a secure message: https://support.patriotgis.com/support/solutions/articles/17000149266-how-an-external-user-can-initiate-a-secure-message


Note: External recipients may also have max size limits configured on their mail servers that dictate how large of an email message that their domain will accept.


Message sent with Outlook Mobile

Microsoft has a hard limit within the policies of the Mobile app itself, to not allow messages with an attachment that exceeds 33MB.