Block certain Domains from accessing a port. How ?

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[lorenzopar]

I would like to block any inbound connection on a certain port when coming from users connected trhouth a certain domain (provider). For example :

block inbound connections on port 25 from users with domain xxx.dsl.telesp.com.br

this means for example   200-204-120-100.dsl.telesp.com.br would be blockedwhen attempting to access port 25, as well as would 201-117-100-100.dsl.telesp.com.br ... etc.

Is this possible using the domain field in rules ??

If yes can you tell me how to build such a rule ??

Thanks

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