I am a mac user, and i use MAIL application to download e-mails onto my computer.

Today i got mails from some intimate dating website confirming and welcoming me for joining etc.

I contacted support to ask for immediate unsubscription, as i don;t want to be in their database, nor use their services, i was travelling in a bus while this was happening.

Then found out that the e-mail subscribed was just like mine but with no dot.

I then sent an e-mail from my e-mail, to this one with no dot, and got it in my mail.

Any ideas how i can fix my problem?

Many thanks

I need to clarify a few things here. Is this a POP account or an IMAP account. Now, you talk about this dot, is it before the @ or after. The Only way I could see this happen is that when the "other" user set up the account, probably IMAP, is he did it with the "no dot" and put in an associated path with your account. A POP account is usually an account given to you by your provider and is rather static by nature.
Your account is absolutely exclusive to you and the only way mail can be directed to your account is if it is sent there, period. Whomever the Provider (domain mane after the @ sign) is responsible. Should this happen on my site, I would rectify the problem as this could turn out to be a very nasty "can of worms". Blacklisting comes to mind for one.