problems sending mail

i get error message.

Client host rejected: cannot find your hostname, [] (in reply

I presume this is a Reverse DNS error.

do i fix this on ubuntu or at my ISP ?

it is on your ubuntu.
most probably, your server cannot resolve hostnames.
this is mostly,
/etc/resolv.conf file
it contains nameserver information
nameserv localhost

Hi ehcpdeveloper,

Seems like the problem was with my ISP.
I have a router with 5 Static IP's, 3 ip's pointed to internal mail servers, with some domains.

I had to ask my ISP to setup reversed DNS for the domains on these 3 ip's.

The mail is going out now with no problem.
It seems like some mail servers look for the reverse DNS before excepting mail, to stop people in sending spam.



Derick Nieuwoudt