Can't Send Email to other domains

[The Unknown]

Hi,
As you know, my system is a mini-Server. I am getting emails directly on my system through my domain.

I am using Sendmail as MTA.

But when I try to send email using the Usermin interface to other domains like Gmail, etc.

I get an IP not authorised error.

What to do ??

Changing MTA shall solve this ??

[mehulved]

Do you have a static IP or a domain name? Dynamic IP's are looked down upon. Also, I believe BSNL's IP range is under blacklist. And have you searched on any search engine for that error?