exclusive sender (right part of address matching)

[SvekY]

I'm NOT talking about domain.com and subdomains subdomain1.domain.com, subdomain2.domain.com matching only domain.com in excl. sender.

I need to ask a what-would-be-if question.
The situation is this:

Facebook sends notifications from facebookmail.com, but a clever system was implemented that uses 5-10 letter string (hash key) assigned to each user in the senders addr. If a spammer finds out I'm on facebook and knows my e-mail, then I will be able to filter non-spam coming from the domain by the hash key.
I would just add in the whitelist that the right part of senders e-mail is "+MY_HASH@facebookmail.com", but how to emulate this in excl. sndr?

First, I had exclusive sender set to facebookmail.com.
Every mail was forwarded and there was no spam sent.

I didn't come to be spamed on the spamgourmet addr, but I wanted to try using this feature Facebook uses, so instead I
set the exclusive sender to +MY_HASH@facebookmail.com.
It produced the same result because I wasn't getting any other mail from that domain but with that hash key.

So, my question is:
Does +MY_HASH@facebookmail.com in excl. sender mean:
anything+MY_HASH@facebookmail.com
OR
anything@facebookmail.com
OR
anything ---because "@" alone means unconditional match, if I understood corectly

Sorry to bother you. I did find a topic about regexp, but I am a n00b in regular expressions, so I require help.

Thanks for answers.

[SysKoll]

The "+" sign has a special meaning in the regex grammar. Try to set your exclusive sender to just YOUR_HASH@facebookmail.com.

[SvekY]

Firstly, sorry for not saying thanks so long. I've been away from internet.

Actually, I did set excl sndr to MY_HASH@facebookmail.com without a "+", but I wrote wrong in the post above.

Now SG seems indicate all mails (and all of them have a hash key) as exclusive sender.

Thanks.