I'm sorry i don't know where is right post.
Now I've user and using outlook express as email client.
few days ago I get same messages with different messages ID sent to recepient, some recepient receive email about 100 or more.
I can't find error messages or warning from server, but i just get some error from outlook express without reason [just error notifications].
Here, I think it's outlook express problem, and now i just find how to blocked same messages subject with different messages id.
I just want to blocked outlook or any email client or user to resend same email with same subject.
[*]*Sorry for my english.