[IMail Forum] 553 Mail box not allowed

[Rafal Karpinski]

One of our clients cannot send mail to us he can receive no problem. He gets following error message 553 Mail box not allowed I couldn't find any reference in the KB  Our system is Imail ver 6.02 running on Dell 2300 128mb of ram, 16 GB HD, NT 4 sp6 Does any one have an idea how to resolve this issue? TIA