Manually tagging contacts in my email marketing provider from my native email browser?

Hi everyone - qq here.

I want to create a quick & simple way to MANUALLY tag contacts in my email marketing provider from my native email browser.

• Ideally the flow would work like this: John @ example. com emails me. From gmail directly, I reply to john and BCC a pre-designated email i.e. tag01@mydomain.com and that email is set up via zapier such that anyone in the [to] field (John in this instance) is automatically tagged with tag01 in my email marketing provider (convertkit in my instance).

• 2nd best flow (and maybe even better / easier?) I create a blank email, copy and paste john@example.com as the subject header and send to tag01@mydomain.com (and same outcome).

The alternative is to go into convertkit / mailchimp / sendgrid / whatever you are using and manually tag people that way - much more hassle.

I can't be the first person to have wanted this - so I figured someone has already rigged this up before? Any pointers would be much appreciated!