While the issue I'm encountering seems similar to many I've seen, none of the solutions I've found has done the trick for me. Lucky me.
I had some trouble but managed to get my 2010 and 2013 clients to connect to the server, and somehow I managed to get 2010 to successfully send mail earlier, but that's not working anymore for some reason. Probably all the messing around I've done with DNS setup.
Every time I try to send mail, whether internally or externally, the event log throw 5016 events at me with regard to not being able to find the "send mail to the internet" connector and the text messaging delivery agent connector - though I've checked in adsiedit and they show up, I'm not sure how to check their health.
When I try to use OWA to send mail, it remains in drafts and I get a 4999 event in the log, as well as periodically receiving 4999's and 10004's related to the EWS url.
I've tried altering the DNS settings from auto to adapter-specific to custom entries, and none of them seems to work. Any assistance would be greatly appreciated, since this is slated to be our new production server as of Monday, and currently while the filesystem and AD are ready, mail is not