Yes we do have mail replica in our IMSA server.
I have Installed IMSA server on top domino server which is sceonddary server.
AS per logs IMSA server trying to access mail file in user home mail server which is primary server.
IMSA server has full access of users mail file.
WE also have connection document between primary and secondary server.
USers are able to sync successfully if I change user home server to IMSA server in person document.