I'm trying to send an OpenPGP-encrypted email from a Linux Mint machine using msmtp, relaying through the smtp server, to another Linux machine, to myself, running Thunde… (read more)
I'm trying to send an OpenPGP-encrypted email from a Linux Mint machine using msmtp, relaying through the smtp server, to another Linux machine, to myself, running Thunderbird (with the sender's (my) imported private key already loaded and working in Thunderbird).
The encrypted test message is composed manually as a file (email.eml) and sent using msmtp from the command line. The email successfully passes through the SMTP relay, is received and decrypted by Thunderbird (so the OpenPGP decryption part works that much I know ... ), but the plain text content is not rendered properly and the email is displayed blank, no plain text as expected. Thunderbird has decrypted the message, but it’s not being displayed or rendered.
This makes me think the issue lies in the structure or MIME headers/parts of the .eml file itself — specifically how the encrypted message body is wrapped. This is not something I'm entirely familiar with, and even less so with what Thunderbird expects for a PGP encrypted message...
I suspect the issue is due to incorrect MIME formatting or missing headers (Content-Type, Content-Transfer-Encoding, Charset, or boundaries etc.) needed for Thunderbird to correctly render the decrypted body into plain text once it receives it. Since I’m assembling the .eml manually (and eventually by a script whej I get to it), I may be overlooking certain structural requirements that typical mail clients (say Thunderbird or similar) or gpg front-ends (like mutt, mailx ...) would handle automatically.
My questions are: Is there a correct MIME structure or format expected by Thunderbird for OpenPGP-encrypted emails ? Is this documented anywhere specifically for Thunderbird ? Or, are there publicly available examples or specs that describe how such an email should be structured (e.g., RFCs or working .eml templates)?
Is there a known way to validate or "lint" .eml files for OpenPGP compatibility ? That would be nice ;-)
As I said the internals or MIME formatting is not my thing usually. Any pointers to Th.B. documentation, sample files, or tools that help with .eml structure validation would be grately appreciated.
Thanks in advance, cheers MM
