I have a Debian machine (actually a Raspberry Pi) that I would like to use as a rudimentary, outgoing-only mail server over a residential connection, just for kicks. Port 25 is blocked. I would like to set it up as a standalone SMTP server, not a relay. Is that possible?
Comcast gives the impression I can use port 587 instead. http://customer.comcast.com/help-and-support/internet/email-port-25-no-longer-supported/
So does this guy (and a few others): http://dragos.fedorovici.com/exim-alternate-port-587/
But this answer https://serverfault.com/questions/452653/many-isps-is-block-port-25-how-do-i-choose-an-alternative-port/ sounds like 587 is only for use within local networks.
Nothing I have tried works. It would be nice to know if the task is possible.
EDIT: I didn't explicitly mention this, but I would like typical mail servers to be able to receive mail that I send from my machine.