Not knowing the details of your environment... Instead of taking on the job of filtering email for all of your clients (this, to me, will open up a can of worms), why not set a policy that port 25 is blocked by default and customers must request for it to be unblocked?
You can then build a list of who may be using your services to send mail and better track if/when undesirable mail is sent from your network? Just a thought. ~ Anthony > From: "Bruno Carvalho" <bruno.carva...@xervers.pt> > To: "SpamAssassin" <users@spamassassin.apache.org> > Sent: Friday, March 22, 2019 9:59:56 AM > Subject: Filtering at border routers: Is it possible? > Hello Folks. > I've just joined this list, i didn't read all rules yet (just some), so bare > with me if my question is misplaced. > I own a small datacenter with 4 uplinks. And i received complains that some of > my clients are using my services for sending spam. > I wanted to know if it is possible to setup spamassassin on a VPS or someting > and have the port 25 redirected to it from border routers. > Important note: I don't know what domains are hosted inside my network. > What i know is that 98% of the spam sent is using port 25. > So, if someone knows a way to filter the mail traffic and block outbound > spam, i > will be thankfull. > Regards > -- > Bruno Carvalho (CEO xervers) | +41 79 884 00 44 > P Please consider the environment before printing this email [ > https://www.xervers.pt/ ] > [ https://www.facebook.com/xervers/ ] [ https://twitter.com/xervers ]
