Exim Relay secondary MX

[explorasrl]

Hi ,
i have this problem

nr2 VPS with DA ,
into VPS1 (hostname : mxfree.mydomain.com ) the mailbox @mydomain.com size 1GB
into VPS2 (hostname : mxpro.mydomain.com ) the mailbox @mydomain.com size 5GB

DNS conf
MX mxfree.mydomain.com 10
MX mxpro.mydomain.com 5

if possible set exim a relay on VPS2 if user not present in VPS1 ?

thanls