how to block someone who uses my e-mail address

[DrWhoF]

as the title.
the story is like this: some dickheads send me doezens of e-mails using my own e-mail address as sender(s).
i looked into properties of this e-mails and it is always different source XXXX.com but all af them lead to canadian pharmacy on-line.
how to block these bustards or how to find out who send this rubish?
please help !!!!!!!!!!!!!!!!!!!!!!!!

 

[dollymitra]

Same happened to my account.changing password had solved the problem .

 

[DrWhoF]

No, it's not the problem with my password.
They just use my e-mail address as the return address.
I can't block my own address.