> On an afterthought, the problem may be solved more elegantly by simply passing the user email and DEFAULT_FROM_EMAIL as context to render_to_string() and then use a custom email template.

Please do this. Why should we force all users to have something prepended to their e-mails even if they don't want to use it? They cannot control the position and nothing, it is hard-coded as it is now. Maybe they are not using Gmail SMTP and don't have this issue, but still are setting `DEFAULT_FROM_EMAIL`.

So I agree from address should go into template context, and can even be in the default template then used, but don't hardocde any strings in the code. This is why we are using templates in the first place.