After Migration, Public Folder Access is asking for Login Credential

Hi Team

Am facing the issue with public folder, after migration to exchange 2013. Users (Outlook 2013 ) are asking for login credential one time during the access of PF from their outlook client (Outlook Anywhere)

we checked one of the affected outlook settings for security tab as mentioned and its mentioned Negotiate Authentication

Here is settings of outlookanywhere 

ExternalHostname                   : webmail.veryzone.com
InternalHostname                   : webmail.veryzone.com.com
ExternalClientAuthenticationMethod : Basic
InternalClientAuthenticationMethod : Ntlm
IISAuthenticationMethods           : {Basic, Ntlm, Negotiate}
XropUrl                            :
ExternalClientsRequireSsl          : True
InternalClientsRequireSsl          : True

While Opening the outlook 2013  or Public folder its popping up one Security Window saying

Connecting to PFMAILBOX2@veryzone.com

User Name

Password

https://social.technet.microsoft.com/Forums/office/en-US/52e2221d-6ab7-43d5-ba5d-245c85d9e81d/after-migration-to-exchange-2013-credential-user-keep-prompting-on-outlook-2010-sp1?forum=exchangesvrclients

i went through the above link, but little bit consfusion as both internal and external hostname has been set