i have installed ms office for mac 2011on macbook air , i have old mails in big archive which was imported from outlook pst files

now my need is i want to import archive mails in to apple mail app,

i trying to drag folders from outlook for mac on dekstop its create .mbox, which was support by apple mail but when i import .mbox in apple mail all mails body and original format show corrupt.

how can i import my archive in apple mail app without corruptions and lost mail?