This can be a particularly nasty one. Whoever is running your mail account is deliberately stopping relaying of mail by the sound of it. There are some very good reasons for doing this, and I can give you an example.
The company I work for has its own domain, etc, and in that domain is a mail server (Microsoft Exchange, as it happens, but this is by and large not relevant)
To allow people outside the office to send and receive mail (eg when travelling) the POP3/SMTP interface is enabled.
By default on Exchange, when you do this you set yourself up as an open relay site. The implications of this are horrendous.
Say you have a domain of mycompany.com, and all the addresses will be
[email protected]
All well and good so far, but anyone who knows you have an open relay could set themselves up with an Outlook express account on their pc to send mail using your mail server as the SMTP host.
They might set up their e-mail address as
[email protected], but the headers on the message trace would show that the message came from mycompany.com
No good for receiving mail, but then this is typically used by spammers to send loads of junk mail (all the adverts for weight loss, xxx sites, etc)
You are inadvertantly hosting loads of spam, and of course if someone complains, the trace leads back to mycompany.com, and you get the blame. Whats worse, is that the complaints are often sent to antispam organisations, such as ORBS, who maintain blacklists.
Once you are on the blacklist (or mycompany.com is) then you will find all your legitimate e-mails being rejected from all over the place, or going down black holes, becuase it is thought to be more spam.
It is for this reason that relaying is prohibited, so you cannot use a server that you don't have an account on to bounce mail around the world, and it seems like the owner of your mail server has implemented tight rules, which are catching you out.
Hope this rather long ramble helps, let me know if you want any more details.
Cheers
[This message has been edited by stickyb (edited 12 April 2001).]