fix(msg): RFC 2047 encode non-ASCII names in address headers#317
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lukas-r wants to merge 1 commit into
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fix(msg): RFC 2047 encode non-ASCII names in address headers#317lukas-r wants to merge 1 commit into
lukas-r wants to merge 1 commit into
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str(NameEmail) emits the display name as raw UTF-8, so To/Cc/Bcc/ Reply-To headers built via ", ".join(str(r) for r in ...) carry raw non-ASCII bytes. On older Python versions the stdlib email package silently re-encoded these (issue sabuhish#225); on Python 3.14+ it no longer does, and some SMTP servers (e.g. Office 365) strip the non-ASCII bytes from the recipient display name and reject the message with `550 5.2.254 InvalidRecipientsException`, eventually throttling the sender. Use email.utils.formataddr with charset="utf-8" so display names are RFC 2047 quoted-printable encoded. ASCII names round-trip unchanged. Also pass charset="utf-8" to the existing formataddr call in FastMail._sender so MAIL_FROM_NAME has the same protection. Fixes sabuhish#316 Refs sabuhish#225
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What
Encode non-ASCII display names in recipient headers (
To,Cc,Bcc,Reply-To,From) viaemail.utils.formataddr(..., charset="utf-8")so they are RFC 2047 quoted-printable on the wire instead of raw UTF-8. ASCII names are unaffected —formataddronly escapes when needed, so existing tests pass unchanged.Reason
Fixes #316 (and addresses the root cause of #225).
str(NameEmail("Lukas Böhm", "lboehm@example.com"))returns'Lukas Böhm <lboehm@example.com>'— raw UTF-8. Older Python versions silently re-encoded such headers; Python 3.14 no longer does. Office 365's SMTP submission server then strips the non-ASCII bytes from the recipient and rejects the message with:Repeated failures push the sender mailbox into a throttled state.
formataddr(("Lukas Böhm", "lboehm@example.com"), charset="utf-8")returns'=?utf-8?q?Lukas_B=C3=B6hm?= <lboehm@example.com>'— RFC 2047 compliant, ASCII-clean.The same
charset="utf-8"is also added to the existingformataddrcall inFastMail._sendersoMAIL_FROM_NAMEgets the same protection.Test
New
test_non_ascii_names_are_rfc2047_encodedintests/test_message.pyasserts that headers for umlaut/diacritic names are ASCII-encodable, contain=?utf-8?MIME markers, and round-trip back to the original Unicode viadecode_header+getaddresses.All 24 tests pass on Python 3.14.