If you put several addresses in the To field, the addresses will be seen by
everyone.
It does not work the way you thought.

Addresses in BCC will not be seen by anyone; addresses in TO will.

Do you know what BCC stands for?

If you want each person's name, and only their name, to appear in the TO
field, you need to send a separate message to each person.  That is the
nature of mail on the Internet.  When you send one piece of mail to
multiple people, they all get identical TO and CC fields.  The only way
to get unique TO and/or CC fields is to send separate messages.  It's
tedious to do that in OE.  There are some bulk mailer programs designed
for this.  You might try the shareware sites.  There are links to
shareware sites in the URL in my signature.  Also, Outlook2000+ can do
this as part of an e-mail/merge.

Send Personally for Outlook Express
http://www.office-addins.com/-outlook-express-addins/send-personally-for-outlook
express.html