Hello,

I am currently running Exchange 2013 CU6. I noticed that clients using POP/IMAP service cannot authenticate to SMTP port 25 of the exchange server, except for users with organization management privilege in ECP. Connecting to port 587 works fine. Telnet to port 25 is successful.

Here are my settings of Default Frontend Receive Connector:

For the Client Frontend:

I seem to recall that in Exchange 2010, connection to port 25 from client is possible. Is this an expected behaviour of Exchange 2013?

Hi 

Can you run Test-PopConnectivity and see the results
Restart your POP3 service and see the results
Check if your POP3 service have valid certificate assigned
Check your ports config and ensure they are correct
Port 110 for POP3 with or without TLS;
Port 995 for POP3 with SSL;


Check the incoming and outgoing mail server in Outlook settings

Incoming mail server box, enter the IMAP or POP server name
In the Outgoing mail server (SMTP) box, enter the SMTP server name

Hello,

As I mentioned before, POP and IMAP connectivity is fine. SMTP connection is fine, provided that port 587 is used. The issue is in port 25.

Hi 

 In your case then you  can enable the trace log and open the log in the location to see for any additional errors.

Please refer to http://technet.microsoft.com/en-us/library/aa997690(v=exchg.141).aspx to set the location and enable the log.

Same problem, which in exchange 2013 they had the same setting as previous (users which authenticate can relay) I can't seem to find this setting in 2013.