In a Microsoft Exchange Server 2013 environment, POP3 and IMAP4 are not supported to use Transport Layer Security (TLS) protocol 1.1 or 1.2.
By design, POP3 and IMAP4 in Exchange Server 2013 support only earlier versions of TLS, including TLS protocol 1.0.
To fix this issue, install Cumulative Update 11 for Exchange Server 2013.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminology that Microsoft uses to describe software updates.