smtp problem in server, cannot find hostname

I am getting this error when i s开发者_Python百科end email by mail function. (ip and emails were hid)

user@server.com R=lookuphost T=remote_smtp defer (-44): SMTP error from remote mail server after RCPT TO:<user@server.com>: host mail.server.com [XX.XX.XX.XX]: 450 4.7.1 Client host rejected: cannot find your hostname, [XX.XX.XX.XX]

any help ?

Thanks

---

It sounds like the remote server is trying to do a reverse DNS lookup of your IP address -- this is typically done as an anti-spam measure. This configuration is the responsibility of the owner of that block of IP addresses -- in your case, probably the ISP that's hosting your server.

---

You can check what reverse DNS shows this way:

$ dig mail.mydomain.com
...
mail.mydomain.com   90  IN  A   74.125.77.121

Reverse lookup

$ dig -x 74.125.77.121
...
121.77.125.74.in-addr.arpa. 86400 IN    PTR ew-in-f121.1e100.net.

So mail.mydomain.com not equal to ew-in-f121.1e100.net - you get blocked.