your thoughts on this common relaying error

[nerdynerd]

Hi,

I have an issue with only 1 domain not able to send my domain emails. Somehow it is my job to fix it. I don't even know what server they are using, but I use domino, with mailmarshal.

What I need to find out first is if it is my end or their end. I think it is there end.. what do you guys reckon?... sorry I don't have any more info, this is all i got to go by at the moment. this is log from their end, there is nothing in my log referencing this that i can find.

2006-05-25 05:43:04 203.67.34.25 MAIL FROM:<them@theirdomain.com>+SIZE=651 31
2006-05-25 05:43:04 203.67.34.25 - 250+2.1.0+them@theirdomain.com....Sender+OK 62
2006-05-25 05:43:04 203.67.34.25 RCPT TO:<me@mydomain.com> 62
2006-05-25 05:43:04 203.67.34.25 - 550+5.7.1+Unable+to+relay+for+me@mydomain.com 78
2006-05-25 05:43:04 203.67.34.25 RSET - 78
2006-05-25 05:43:04 203.67.34.25 - 250+2.0.0+Resetting 93

thanks guys.