Create Email/set metadata directly, avoid parsing the generated raw message to obtain it.

[mdecimus]

Issue: Currently when a message is created using the Email/set method, for simplicity reasons the message metadata is created by parsing the raw message generated by mail-builder.

Fix: Avoid this performance penalty by directly creating the message metadata.

[dumblob]

I would guess this penalty is much less of an issue than most other tickets in this tracker 😉.

Actually paying for slightly more performant CPU is usually much cheaper than waiting for this optimization to land (assuming sane project management which will prioritize other really important features before this minor perf optimization).