Exchange 2013 and 2010 co-existence, The mailbox of user that is located on a server that is running version 14 can't be opened on a server that is running version 15.

Dear Team,

I am facing a strange issue we are running exchange 2013 with 2010 in co-existence mode,we are in the process of migration mostly all the mailbox are migrated to exchange 2013.

when one of the exchange 2013 user is trying to send an email to another user whose mailbox also exists in exchange 2013 he is getting the below bounce back message.

HAMM.abc.com Remote Server returned '554 5.2.0 STOREDRV.Deliver.Exception:NotSupportedWithServerVersionException; Failed to process message due to a permanent exception with message The mailbox of user mkh@abc.com that is located on a server that is running version 14 can't be opened on a server that is running version 15. NotSupportedWithServerVersionException: The mailbox of usermkh@abc.com that is located on a server that is running version 14 can't be opened on a server that is running version 15. [Stage: CreateSession]'

Thanks.

TechGUy,System Administrator.