After working OK for 3 weeks or so, the POP and IMAP connections started failing. In a running client, it adds the error code 0x800CCC1A. When the server was first installed, it started doing that and it was resolved when I installed a valid CA certificate. Outlook Anywhere and OWA continue to work, both inside and outside, and we never get any certificate mismatch errors. Oddly enough, I can send email with a POP (or IMAP) account but not receive. Since this seemed to point to the certificate, I have double checked it. There are 4 certs, 3 are self signed: the Exchange Server Auth, Exchange Delegation and WMSVC. The 4th is the SAN cert, from a CA. I removed all services from the 3 self signed certs and the CA cert has all 4 services. The Auth Cert keeps giving itself back the SMTP but the failure occurs even if I remove that cert.  I have not found any errors in the event log that match the time of testing. 

We are running Exchange 2013, CU7, on  a 2012 R2 Std Server. The DC is a 2012 R2 Essentials server. 

Any suggestions appreciated.

Hi Lou,

According to your description, I understand that POP account cant receive message with error 0x800CCC1A, however it can send message without error.
If I misunderstand you concern, please do not hesitate to let me know.

I want to double confirm whether all POP3 account or some special account experience this issue?
Error 0x800CCC1A means that the Secure Sockets Layer (SSL) encryption is turned on for your e-mail account or firewall prevent.

Please try to disable SSL to test: File---> Account Setting---> Change, switch to POP3 and IMAP setting then disable SSL.
If the issue persists, please try to run below command to ensure whether SSL or TLS is used for POP3:
Get-PopSettings Server server1 | FL Identity, X509CertificateName

Best Regards,
Allen Wang

Dear 

i am facing similar problem i just want to configure pop3 (PST) account not OST account but cant configure please help me out with video or image configuration or step by step some help

Regards,

Muhammad Kamran Ashfaq

Thanks. This is all accounts on the Exchange server. These were all working OK (most are outlook anywhere, which is still working OK). Removing SSL doesn't work because Exchange (2013) will not allow non secure connections. Again, this changed soddenly. I am going to remove all of the recent updates on the Exchange server to see if they broke anything. 

If I create a new POP or IMAP profile, it does the same thing. Again, I can create an Outlook Anywhere account OK.