I changed an MTA in postfix from sendmail, but two same email contents arrive when the same address is included in To and Cc. There did not need to be such email contents, Please Help me!. with the avoidance of this movement at the time of sendmail.
To work around this we have moved all mbox-to-mbox aliases into virtual and have set:
enable_original_recipient = no
So that all the 1-to-many expansions are done in virtual and aliases is only used for single delivery to commands or files.