Request for assistance

[Mark Glassberg]

I've been looking for a new isp and tried intergate.com.  They don't
support linux, but everything went well until it came to sending mail.
After much experimentation, it seems that their smtp service only
recognizes mail where the domain of the sender is that of their dns'.
Two questions:  Does this observation/conclusion make any sense?  If
so, is there anything I can do to get my mail accepted?

Any assistance will be greatly appreciated.