I'm using flask-mail, which calls email.utils.make_msgid() to create unique ids for emails. On a heroku flask webapp, messages come through to a GMail account with an updated message-id indicating Google thought the id was broken and updated it. I have seen delivery problems to hotmail/outlook, and wonder if this could be related.
What about the id makes Google think it's broken? Should I be generating my own ids and overriding the mail library?
Message-ID: <[email protected]>
X-Google-Original-Message-ID: <152467882097.8.1913443827376089096@21e56170-89b2-40e3-a2a0-830f26b2fb11.prvt.dyno.rt.heroku.com>