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Verizon is blocking TCP port 25

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TedNJ
Contributor
Contributor
Posts: 2
Registered: ‎12-23-2017

Verizon is blocking TCP port 25

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I have been trying to resolve an issue where my mail client cannot connect to any server on tcp port 25.  I have attempted to use a number of different relay servers as well as my employer's server.  They are all being blocked.

 

Verizon is denying this is the case.  I even had one of their support personel tell me the issue is because my IP address is black listed.

 

I know this is not the case though since I can telnet to my employers server on another port that is used by mail services.

 

Are any of you experiencing the same issue?

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JustinG
Silver Contributor V
Silver Contributor V
Posts: 404
Registered: ‎07-29-2015

Re: Verizon is blocking TCP port 25

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Hello!

 

Yes, I can confirm that Verizon does indeed block port 25. And so does most other residential Internet Service Providers. Often level 1 tech support isn't 100% accurate, here is the Verizon page stating the details of the block: https://www.verizon.com/support/residential/internet/highspeed/general+support/top+questions/questio...

 

Does your work offer the option of using the SMTP standard client port of 587 (or 465)? If not, this is an issue that they need to fix, since you won't be the only user who runs into this problem. 

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JustinG
Silver Contributor V
Silver Contributor V
Posts: 404
Registered: ‎07-29-2015

Re: Verizon is blocking TCP port 25

Message 2 of 2
(7,430 Views)

Hello!

 

Yes, I can confirm that Verizon does indeed block port 25. And so does most other residential Internet Service Providers. Often level 1 tech support isn't 100% accurate, here is the Verizon page stating the details of the block: https://www.verizon.com/support/residential/internet/highspeed/general+support/top+questions/questio...

 

Does your work offer the option of using the SMTP standard client port of 587 (or 465)? If not, this is an issue that they need to fix, since you won't be the only user who runs into this problem. 

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