Office 365 cannot receive a 25 MB email attachment

A few weeks ago one of our principals was working on a presentation for a conference with a few folks outside of our organization. He was trying to exchange PowerPoint slides with these individuals but ran into problems. I believe there was an issue with the attachment size. I say believe because the senders did not receive a non-deliverable message and due to the nature of the circumstances (the last few days before a conference) was not able to contact the senders to discuss the file they sent.

I've tested the ability of my account to receive large files and the largest file that make it trough is 21 MB. After that, nothing. No NDR to the sending account, no failure message to the receiving account, just nothing.

I opened a case with Microsoft and they were unable to resolve the issue. Or I should say they were unable to contact me...