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Are there special considerations for opening port 587 on a firewall?

Posted on 2016-10-28
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Last Modified: 2016-11-16
Our ISP has required us to switch our SMTP traffic from port 25 to 587.  (Interesting note: We are a business with a business account.)

I have duplicated the STMP configuration lines in our firewall, replacing “SMTP” with “587”.  I think the port is now open.  

Someone claims they are not seeing traffic sent on port 587, and has asked us to prove it is not an issue on our firewall.  We are receiving traffic on port 587.  

Would there be additional steps after opening the port such as setting some kind of authentication or encryption in the firewall for port 587?
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Question by:tmaususer
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Author Comment

by:tmaususer
ID: 41863828
This is the config:

access-list 101 extended permit tcp any host xxx.xxx.xxx.xxx eq smtp
 static (inside,outside) tcp interface smtp xxx.xxx.xxx.xxx smtp netmask 255.255.255.255

 access-list 101 extended permit tcp any host xxx.xxx.xxx.xxx eq 587
 static (inside,outside) tcp interface 587 xxx.xxx.xxx.xxx 587 netmask 255.255.255.255
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Jan Springer earned 500 total points (awarded by participants)
ID: 41863859
If you have a mail server and you are a business, you need port 25 open and your provider should  honor that.

If you don't have a mail server and you want to send outbound mail relayed through an external server, your provider may be asking you to send that mail via port 587 (the submission port).

At any rate, if the email is outbound only, your firewall shouldn't need to be changed.
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Author Comment

by:tmaususer
ID: 41863870
Thank you,
They have refused.  They say they are doing this for all accounts - business and residential, weather or not they host our email or domain.  We have talked to them 5 times to verify.  Many people have said this is extreme.  
Yes, we host our own email server onsite.
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by:Jan Springer
Jan Springer earned 500 total points (awarded by participants)
ID: 41863957
Seriously, if you have an internal mail server, then change providers.

This is worse than ridiculous.
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Author Comment

by:tmaususer
ID: 41863961
We want to.   Unfortunately, there are no options in the area.
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Expert Comment

by:Jan Springer
ID: 41863974
So, between DSL, wireless, cable tv, ethernet, and ftth there is but one option?

I know some rural areas lack competition but -- no one else?
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Author Comment

by:tmaususer
ID: 41863981
Well, we don't want DSL. I am going to check windstream and level 3.  Cable is monopolized by the same company giving us trouble.  what is ftth?  Would Ethernet be direct site to site?
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Expert Comment

by:Jan Springer
ID: 41863992
fiber to the home.  and yes, ethernet, with or without switching, is site to site.

definitely call windstream and l3.

this company does not deserve your business.
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Author Comment

by:tmaususer
ID: 41863994
we are a business
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Expert Comment

by:Jan Springer
ID: 41863997
by "this company" i mean "your provider".
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Expert Comment

by:Jan Springer
ID: 41889425
Opening port 587 is similar to opening port 25.

However, port 587 is the client submission port -- not the port to use as a mail transport agent speaking with other mail servers for the final delivery of email.
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