Modify header field or subject

[caco3]

Is there a way to modify the subject or add/modify a header field?

I am building a spam filter and need to add the score somehow to an email.

Eg (Header):

X-Spam-Score: 20

or, if this is not possible, it could be added to the subject:

***** SPAM ***** (10.8) ***** Newsletter abcd

[mjs]

I'm afraid this isn't really possible. IMAP messages are basically immutable.

The best you can do is download the entire message, modify the headers and append it to the mailbox, and then delete the original one.

This Stack Overflow questions covers the topic: https://stackoverflow.com/questions/16945041/imap-editing-a-draft-or-existing-message

[caco3]

Thanks for the explanation.
I actually expected something like this :(

[mjs]

With the append method: https://imapclient.readthedocs.io/en/2.2.0/api.html#imapclient.IMAPClient.append

APPEND is the IMAPClient command for adding a message to a mailbox.