I'm trying to create a custom webmail, for one of our products, that has thousand of users.
We would like to create the webmail by our own, and let the user sends it by his/hers personal email (One that they already have, and is created)
I know that HubSpot CRM has something like that, but i don't know what i should be aware of, or how i can do it.
I know there I's a lot with spam, reputation etc, but i need some guidance. Can anyone help me out?
It could be awesome to do it with SendGrid integrated.