Avatar of Hayden Wells
Hayden Wells

asked on 

Exchange 2013 refusing some SMTP connections but allowing others using anonymous receive connector

I have a single Exchange 2013 server, running for 6 months. We have several servers/devices that anonymously relay through it which are working fine. I attach screenshots of the FrontendTransport connector settings showing my PC in the list of allowed IPs.
User generated imageUser generated imageUser generated image
I've tried to Telnet to it on port 25 but get refused.
    Microsoft Telnet> open 25
    Connecting To not open connection to the host, on port 25: Connect failed
    Microsoft Telnet>

I've added two new IP addresses to the list of IPs in the receive connector but these two devices are being denied connection. The others are all still working fine.

    220 mail1.bywaters.co.uk Microsoft ESMTP MAIL Service ready at Tue, 2 Feb 2016 1
    2:03:39 +0000

The Application log doesn't show me anything, the SMTPReceive Protocol logs do not contain the source IP address of the failed connection., Windows firewall is disabled on the Exchange server. I have restarted the Exchange server with no effect.

Can anyone suggest how to proceed with fault finding? Or if you've solved a similar problem?

Avatar of undefined
Last Comment
Hayden Wells
Avatar of Gilbert Hauser
Gilbert Hauser
Flag of Switzerland image

Could you give more informations concerning your network topology?

You are using different network, from the range what kind of router are you using to reach the
Avatar of Hayden Wells
Hayden Wells


Thank you for your quick response.

There is no router between the clients and the server, I'm using a 22 bit SM on a single LAN.

My subnet includes using SM:
Avatar of Gilbert Hauser
Gilbert Hauser
Flag of Switzerland image

Blurred text
View this solution by signing up for a free trial.
Members can start a 7-Day free trial and enjoy unlimited access to the platform.
See Pricing Options
Start Free Trial
Avatar of DLeaver
Flag of United Kingdom of Great Britain and Northern Ireland image

I recommend this tool to give you a more specific output than telnet - https://www.microsoft.com/en-gb/download/details.aspx?id=17148

Run it from your PC to Exchange, the command line version is excellent.
Avatar of Hayden Wells
Hayden Wells


Solved thanks to Gilbert.

The important part of your post was "your computer is authorized to use the port 25".

This made me look at the client which, although Windows Firewall is disabled, was being prevented from sending SMTP due to McAfee AV. Disabling the "Prevent mass mailing worms from sending mail" solved the issue.

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Top Experts
Get a personalized solution from industry experts
Ask the experts
Read over 600 more reviews


IBM logoIntel logoMicrosoft logoUbisoft logoSAP logo
Qualcomm logoCitrix Systems logoWorkday logoErnst & Young logo
High performer badgeUsers love us badge
LinkedIn logoFacebook logoX logoInstagram logoTikTok logoYouTube logo