Creating an attachment in encode(_:, composeContext:)

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Created Jan ’22

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It seems that the mail app sets its mail headers after additionalHeaders(for:) is called, overwriting standard headers set by the extension, such as Content-Type.

It also seems the Mail app decides whether an email is of content type text/plain or multipart/alternative; boundary="Apple-Mail=[...]" based on the user input. If the user only inputs plain text (i.e. using no font formatting options or adding an attachment) then Content-Type will always default to text/plain.

This causes an issue in encode(_:, composeContext:) if the signature should be included as an attachment. First of all, it seems impossible to force Mail to set Content-Type to multipart/alternative and even if the message is set to multipart/alternative (e.g. b/c the user made text bold), the ecode method doesn't know the boundary string set by Apple mail (Apple-Mail=[hash]).

Is there a way to create an attachment in encode?

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Answer 1

PuzzleMaster OP

Jan ’22

Maybe I should rephrase the question. In PGP/GPG the signature and the encrypted message are usually embedded as attachments in the email. This way, a recipient that doesn't have PGP/GPG installed (anymore) will see an empty email with an encrypted.asc file instead of the encrypted gibberish in the body of the email.

I'd like to do the same as PGP/GPG and store the signature and the ciphertext in an attachment. How do I do that?

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