unable to connect to exchange server

[adnankhazaleh]

the customer used microsoft exchange server 2010 hosted and managed by the goverment  to send and recived mails using both web browse or outlook application isntalled on endpoint machines without any issue .

last week , microsoft exchange server upgraded to exchange server 2016 , and from this point they are facing connection issues with exchange server when proxy setting configured on endpoint device .

when the customer tried to add new profile to mail client when the proxy setting applied , connection to exhange server failed and adding profile failed , when the customer remove the proxy setting and go direct , adding the profile on mail client works fine .

we tried to add test client IP as whitlisted (stop cycle) to bypass MWG polices , also URLs used by exhange server added to whitelist and the same issue happened again