If you run your own mail server, you can usually configure it to forward mail over SMTP to a specific port, rather than delivering it to a mailbox for a client

If you run your own mail server, you can usually configure it to forward mail over SMTP to a specific port, rather than delivering it to a mailbox for a client to pick up using IMAP. If you send the mail (using SMTP) to inbox.py, you'll get callbacks as soon as the mail is received, without having to worry about mailbox management and the complexity of an IMAP client.