procmail auto-encrypt

.gpg-mime-end

--MfFXiAuoTsnnDAfX

.gpg-mime-start

This is an OpenPGP/MIME encrypted message (RFC 4880 and 3156)

--MfFXiAuoTsnnDAfX
Content-Type: application/pgp-encrypted
Content-Disposition: attachment
Content-Description: PGP/MIME version identification

Version: 1

--MfFXiAuoTsnnDAfX
Content-Type: application/octet-stream; name="msg.asc"
Content-Description: OpenPGP encrypted message
Content-Disposition: inline; filename="msg.asc"

.procmailrc

# Thanks to <https://www.j3e.de/pgp-mime-encrypt-in-procmail.html>
:0 H
# modify your filter, which mails to encrypt, here:
* ^Subject: encryptme
{
	MYHDRS=`formail -XContent-Type: -XContent-disposition: -XContent-transfer-encoding:`
	# replace with your PGP key ID here:
	RECIPIENT="1C17FF57D51F1277304905DA9C63B7474B4D9FB5"

	:0 fh
	| formail -I 'Content-Type: multipart/encrypted; protocol="application/pgp-encrypted";boundary="MfFXiAuoTsnnDAfX"' -I Content-transfer-encoding: -I Content-disposition:

	:0 fb
	| { cat ~/.gpg-mime-start ; { echo "$MYHDRS" ; echo ; cat - ; } | gpg --batch --quiet --always-trust -a -e -r ${RECIPIENT}; cat ~/.gpg-mime-end; }
}