Exchange 2016 stuck on send mails after port 25 has been block by my ISP

MikeZetPOL 41 Reputation points
2021-10-26T13:09:46.073+00:00

Good Morning everyone.

So I just noticed big queue in my mails to external servers. After fast investigate I noticed blocked port 25 here:
143851-2021-10-26-14-51-17.png

Fast call to my ISP and just got straight answer that my ISP block this port for security reason since last night.

So I started to looking for a solution - eg. change port to 587 and found some articles about that. In fact my mail server had used port 25 to send mail outside. I use command: 

Get-SendConnector | fl port

with bring: "Port : 25".

So my next step was change it to 587: 

Set-SendConnector "My.Domain.Name" -Port 587

And reboot.

Unfortunately I have still issue to send mail outside my exchange server. I receive that type of errors here:

2021-10-26T12:19:04.508Z,MyDomain.Name,08D9987A111B2A02,2,,142.250.115.26:587,*,,"Failed to connect. Winsock error code: 10060, Win32 error code: 10060, Destination domain: gmail.com, Error Message: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 142.250.115.26:587."

143847-2021-10-26-15-24-05.png

I rebooted server twice, also, flushed DNS cache.

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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Accepted answer
  1. Andy David - MVP 142.2K Reputation points MVP
    2021-10-26T13:35:05.543+00:00

    The only thing I can think of is using a 3rd party SMTP service that you connect to as a smarthost ( typically on any port) and then they relay your messages on port 25 to external domains.

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  1. Andy David - MVP 142.2K Reputation points MVP
    2021-10-26T13:26:14.27+00:00

    Port 587 is a client submittal port and typically requires the sending client to authenticate so that probably wont work.

    You will need to get a static business level IP so your ISP wont block it.