SMTP server does not let me send mails

Hello everybody. I want to use my own mail server address to send and receive mails. But my ISP does not let me do that. I carried out a test also to check if they block SMTP 25 by typing 'telnet smtp1.arian.net 25' into 'run' in start. And it confirmed that my ISP (mtnl) does not block SMTP.
Everytime when I try to send the mail, it shows that the mail is going but when it finieshes, it showes the followoing error:
The message could not be sent because one of the recipients was rejected by the server. Server Response: '554 <receiptent@mailaddress.com>: Receipent address rejected: 'smtp.domainname.com', Error Number: 0x800ccc79).

There is no problem in receiving the mails. I get the above message when I try to send the mails through my mail server using Outlook Express.
I tried to change it with my ISP smtp server. But that also did not work.

I would be very greatful to you if any of you can help me out.
Kind regards,

Hi

I'm a hosting manager/administrator and we often have such problem with our customers. Many hosting companies run alternate SMTP servers (for example on port 2567 or 6547 etc.) and we advise our customers to use this our SMTP server.

Another way to solve this issue is to use sock-proxy server, but is way is not to easy.