I set up a web site for a friend on my server. I also gave him an e-mail account using his new domain name.
When my friend tries to send e-mail through his dial-up "mom & pop" ISP's SMTP server using his new e-mail address, they reject it, saying they don't relay e-mail for the address he is trying to send to. By contrast, my ISP gives me no problems when I do it.
Main question: Is there a way to safely let my server relay e-mail for him so he can send mail out using his new e-mail address? I'm using postfix.
Curious question: It seems pretty restrictive to allow your users to send e-mail using only the e-mail address you give them as an ISP. What's their problem?