can not archive moved Mail Items From PST

Hi,

I want to learn something about archiving strategy. I assume the create policy as "Archive Mailbox Before 6 months" And it's working successfully.

BUT ;

I Moved or Copied old mail ( old from 1 years ) items from PST file to My Exchange Profile. But it's not archived.

I noticed that this mail items "modified date" date is changing.  is this correct ? Is this Issue ?

what is your comment about this  ?

Notice ; I don't want to use Enterprise Vault "PST Archiving Option".Only I want to learn my method is works or not works.If not works I'll use PST Archiving Option.

Thanks