On Thu, 2006-11-02 at 14:43 -0800, Marc Perkel wrote:
The reason for this is that I think that the elimination of SMTP from the client is a big step to control spam. The idea being that if IMAP can transfer outgoing mail the SMTP wouldn't be necessary for clients and we can block port 25 on windows machines and viruses can't send email. And the virus wouldn't have access to the IMAP password so viruses can't authenticate to send mail.
Here in Finland port 25 is already blocked by all the major ISPs. Only the ISP's own SMTP server can be used which also typically limits how fast mails can be sent through it.
I'm using submission port (rfc2476) nowadays for sending my own mail to my SMTP server. Submission port in general is supposed to require authentication from clients.
I think using the submission port is just as good for blocking spam as it would be to send mails via IMAP. Both work only as long as viruses don't use your email client directly and don't dig up the password from the client's configuration.