When we try to create message with attachment which is near 10mb (Word document) we caught 400 Broken Pipe.
Error

Body example.
https://drive.google.com/file/d/1t-Yx0LUN9yr1aUorTsROJCNztqNoKtSr/view?usp=sharing
Endpoint:
https://graph.microsoft.com/v1.0/users/igogo@talando.onmicrosoft.com/mailFolders/AAMkADNhOGEwNDcwLTNiYzgtNDhjNi1iN2EwLTExNDAzZTExNWQwOQAuAAAAAAAKf5RtCz4WR7os4poWtKnCAQBEW26C7Or7S4A49CE-v02RAAADOx3nAAA=/messages