101 can call 102, but not 103.

[ipSkillz]

Hi.

I've built an Answering Server for voIP pabx's that works very well.

I have my pc siphone setup as extension 101.
The Answer Server on extension 102.
And an additional 3rd party server on 103.

101 can call my server perfectly, but just rings when trying to contact 103.

Any help?

Thanks.