SMTP code 250 but email lost at remote server

Question

I'm experiencing a weird issue with my mail server. Currently i'm using Apache James as a relay to dispatch emails to an external mail server. Sometime it happens that even if I receive an SMTP code 250 from the external mail server, the email diasappears and never get delivered or it is delivered after a very long time. Point is: am i right assuming that until i receive the SMTP code 250 of successful delivery from the external server, it is not a problem of my mail server?

Answer 1

Even you get SMTP return code 250, it doesn't guarantee your email will arrive in final destination.

That return code means that the relay server ACCEPTS your email-delivery request. After they accept the request, who knows what happen after that. Several possibilities:

1. The remote server scan your email with AntiSpam daemon and (unfortunately) your email is mis-idenfified as spam. So they discard/drop it.
2. The remote server just don't like your email. Maybe your IP Address blacklisted. So they silently discard it.
3. The remote server is busy processing other jobs. So they delay your email delivery.
4. The server happily to forward your email to final destination right now.

Further info: Simple_Mail_Transfer_Protocol on Wikipedia