- Shipped
- November 13, 2026 at 8:06 AM UTC
- Author
- Kamo
- Commit
- 59ebbd3
GraphMailProvider posted the whole MIME base64 to sendMail in one call. A file is base64 twice on that path (inside the MIME, then the MIME itself, ~1.82x), and Graph refuses a request over 4 MB, so about 2.2 MB of attachments was the ceiling; a 3 MB PDF was a ~5.5 MB request. Proven by GraphMailProviderLargeSendTest. Messages over the one-call cap are now drafted from MIME without their files (threading, inline images and our Message-ID kept), each file attached on its own (upload session in 3.75 MiB chunks above 3 MB, up to 150 MB per file), then sent with /send, which files the copy in Sent Items as sendMail did. Drafts use the same path without the send. A failure part-way deletes the half-built draft. Small messages keep the single sendMail call. DL0.1, DL0.2