Post Office Duplicates Mail

The post office appears to have an issue where incoming, external
internet mail is duplicated for each internal recipient for as many times
as there are internal recipients.

eg
if external user xyz@gmail.com sent an email to user1@beattie.co.nz,
user2@beattie.co.nz and user3@beattie.co.nz making the total amount of
beattie.co.nz recipients three

then the post office would deliver the same external message from
xyz@gmail.com three times to each of the above beattie.co.nz recipients.