Hi, I'm not fully up-to-date on the issue, but I did have this note in my archives, which I can't find the original source, but here it is:

  Non USASCII characters *in headers* require special encoding:
  
  1)
   use Encode;
   $x="....";
   $x_for_header = Encode::encode('MIME-Q', $x);
   
    MIME-Q is the best for mostly USASCII strings
    MIME-B is the best for mostly non USASCII strings
   
    2) 
    Add one extra header to *fully* declare body encoding:
    print MAIL "Content-Transfer-Encoding: 8bit\n";
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Hope it helps.