If I block port 25, am I safe against spammers?

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Posted by v33usa, 08-07-2013, 08:47 PM
Hello guys, I've got a question. We offer online workstations (RDP). Users use these workstations to work, but they certainly don't need them to send emails. We'd like to get our butt covered against possible spammers abusing the workstations, so we thought about blocking port 25 in our firewalls. Would this be enough? Can spammers use another port to send emails? I know that there's also port 587. Would this be a good way to prevent spammers from abusing our system? Thanks.
Posted by FR-Ammar, 08-07-2013, 08:56 PM
Does your firewall support DPI? Use that to block SMTP traffic.
Posted by MikeDVB, 08-07-2013, 08:56 PM
Blocking 25 will stop them as acting as a MTA [Mail Transit Agent]. Connecting to port 587 would be done as a client - usually requiring a username and password or prior authentication.
Posted by net, 08-07-2013, 08:57 PM
Moved > Hosting Security and Technology.
Posted by monitorscout, 08-08-2013, 09:48 AM
Yes I completely agree with MikeDVB
Posted by BestServerSupport, 08-08-2013, 11:16 AM
Setting up 587 is a good idea but you should also take care of following points: 1. Enable SMTP authentication. 2. SPF record setup. 3. DomainKeys setup. 4. Enable RBLs. 5. Prevent Nobody user to send out emails.
Posted by ttgt, 08-08-2013, 11:17 PM
so,port 587 is better than 25 ?