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Sammanfattning: Addition of code to give a name to the pgp-signature MIME part of the message.
Tillagd:
> The problem seems to be that Outlook doesn't like unnamed attachments. Using the following code (based on settings from Sigma [https://github.com/sigma/dotfiles/blob/master/_gnus.el]), Gnus gives the attachment the name "signature.asc" immediately before sending:
> (defadvice mml2015-sign (after mml2015-sign-rename (cont) act)
> (save-excursion
> (search-backward "Content-Type: application/pgp-signature")
> (goto-char (point-at-eol))
> (insert "; name=\"signature.asc\"; description=\"Digital signature\"")))
> ----
There are some PGP plugins for outlook which may be able to decrypt the message you send them with PGP/MIME, but encrypted attachments will show up in outlook with a random name and the file extension .dat.
When searching the interweb for help I found lots of rants and just a few hints[1][2], thus I will describe a workaround.
First of all, install MailCrypt.
Then add this elisp code to your ~/.gnus.el.
;; "put Content-Type: text/plain at top of empty parts" (gnus manual) (setq mml-insert-mime-headers-always t)
;; encrypt always with my key (setq mc-encrypt-for-me t)
;; don't sign the message (setq mc-pgp-always-sign 'never)
The problem seems to be that Outlook doesn’t like unnamed attachments. Using the following code (based on settings from Sigma [3]), Gnus gives the attachment the name “signature.asc” immediately before sending:
(defadvice mml2015-sign (after mml2015-sign-rename (cont) act)
(save-excursion
(search-backward "Content-Type: application/pgp-signature")
(goto-char (point-at-eol))
(insert "; name=\"signature.asc\"; description=\"Digital signature\"")))