I can successfully send and receive messages from my dyndns hosted domain name. There are issues, but it does work.
* Home based server behind an ISP firewall
* Ubuntu 6.10 with splitdns configuration
-- Configured as a domain name that I have registered
-- external zone should never be seen by the outside world
* Dyndns using a custom dns service ($)
-- pointing my registered name at my current isp assigned address
-- A dyndns updater client running to keep the ip's in sync
-- (No reason to believe the free dyndns hosts wouldn't work)
Currently, my outbound messages are frequently rejected or spam filtered by receiving mail host due to (I presume) lack of credible hostname resolution. I may need to use my outbound ISP smtp (if it will allow relaying) or I can set up MailHop Outbound ($).
My inbound port 80 is blocked, my inbound port 25 is NOT. Your mileage may vary. I can use mydomain.org:8080 (works now) or use WebHop to cloak the port mapping (in progress.)