Application could not use POP3 in Exchange

Hello all,

I'm running into some issues with an application that could connect to POP3, but is getting error "-ERR Command is not valid in this state" when tried to login. Things I have checked:

• POP3 and POP3 Backend: set to automatically running
• PopProxy: running
• Logon type: I tried using all 3 types (Secure TLS,Integrated Windows Authentication,Basic Authentication)

Other commands that I tried running was:
Test-PopConnectivity

RunspaceId                  : 3ffa4789-ed9e-4021-a401-d20e980cf665
LocalSite                   : Exch01
SecureAccess                : False
VirtualDirectoryName        :
Url                         :
UrlType                     : Unknown
Port                        : 0
ConnectionType              : Plaintext
ClientAccessServerShortName : Exch01
LocalSiteShortName          : Exc
ClientAccessServer          : Exch01.domain.net
Scenario                    : Validating User object.
ScenarioDescription         : Create Active Directory User objects.
PerformanceCounterName      : POPConnectivity-Latency
Result                      : Failure
Error                       :
UserName                    : exchtest2
StartTime                   : 9/18/2019 2:00:20 PM
Latency                     : -00:00:00.0010000
EventType                   : Error
LatencyInMillisecondsString : -1.00
Identity                    :
IsValid                     : True
ObjectState                 : New

testemail
E:>testemail 10.10.01.01 110 user01 password  pop3 true
** Email test: Connected to e-mail accountuser01
DEBUG: setDebug: JavaMail version 1.3.2
DEBUG: getProvider() returning javax.mail.Provider[STORE,pop3,com.sun.mail.pop3.POP3Store,Sun Microsystems, Inc]
DEBUG POP3: connecting to host "10.10.01.01", port 110, isSSL false
S: +OK The Microsoft Exchange POP3 service is ready.
C: USER user01
S: -ERR Command is not valid in this state.
C: QUIT
S: +OK Microsoft Exchange Server 2013 POP3 server signing off.
javax.mail.AuthenticationFailedException: Command is not valid in this state.
        at com.sun.mail.pop3.POP3Store.protocolConnect(POP3Store.java:159)
        at javax.mail.Service.connect(Service.java:233)
        at javax.mail.Service.connect(Service.java:134)
        at javax.mail.Service.connect(Service.java:86)
        at psdi.tools.TestEmail.<init>(TestEmail.java:100)
        at psdi.tools.TestEmail.main(TestEmail.java:52)


Is it possible that having 2 certificates with POP services assigned could cause this issue? Otherwise, I'm not sure what else I need to check.