How to Connect Mailgun/Sendgrid/other Email with no IMAP

Boxward maintains a 1-to-1 sender to recipient ratio. If you’re using an SMTP service (like Mailgun, Sendgrid, etc.), you will still need an inbox for IMAP so that you can receive emails and participate in the warmup network. This does not have to be the same email address. For example, you can use a personal Gmail address for the IMAP connection.

More info here.