Blocking Port 25 / Only Using Port 587?

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bellaonline
Posts: 107
Joined: Tue Feb 28, 2006 7:15 am

Blocking Port 25 / Only Using Port 587?

Post by bellaonline »

I recently had a spammer get a hold of one of my email account passwords and send a boatload of spam through my system before we caught them. As part of the triage, my hosting company is recommending I completely block / close port 25 and only use port 587.

My understanding was that port 25 was for non-SSL incoming SMTP and that port 587 was for SSL incoming SMTP and that it was good to have both as an option.

Thoughts? Would I run into trouble if I completely closed off 25 and only had 587 open? I did try to search for an answer on this but wasn't able to find something on this particular question. Maybe I didn't use the right phrase.

MailEnable-Ian
Site Admin
Posts: 9738
Joined: Mon Mar 22, 2004 4:44 am
Location: Melbourne, Victoria, Australia

Re: Blocking Port 25 / Only Using Port 587?

Post by MailEnable-Ian »

Hi,

If you block port 25 inbound you will not be able to receive emails from remote mail servers as all mail server send/receive over port 25. Please review the following article which explains the best practices for securing the MailEnable services:

https://www.mailenable.com/kb/content/article.asp?ID=ME020727
Regards,

Ian Margarone
MailEnable Support

dcol
Posts: 237
Joined: Fri May 26, 2017 11:25 pm

Re: Blocking Port 25 / Only Using Port 587?

Post by dcol »

But, what if I want to block port 25 from outgoing mail? Lots of attempts here to try to send email via port 25 from spoofed users. All my users are set to send via SSL port 465. I do not want any one to send mail via port 25.

Admin
Site Admin
Posts: 1127
Joined: Mon Jun 10, 2002 6:31 pm
Location: Melbourne, Victoria, Australia

Re: Blocking Port 25 / Only Using Port 587?

Post by Admin »

Hi,

You can do this under the port settings for the SMTP Inbound. Change the drop down for port 25 to be "Never allow authentication". Then only emails for local addresses will be accepted through that port unless you have allowed them to relay via IP address.

dcol
Posts: 237
Joined: Fri May 26, 2017 11:25 pm

Re: Blocking Port 25 / Only Using Port 587?

Post by dcol »

Yes, I saw that when poking around. Thanks

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