Hi Scotty,
Is there a way I can hide email addresses/recipients on outgoing messages?  I get some from friends saying "Reply to" and their name.  Or "undisclosed recipients".  I looked on Mail Preferences and found only how to hide email addresses in a group.
Hope you are doing well, and thank you in advance.

Yes, the way to go about this is to send the email out to one person only (can be yourself) then put the rest of the recipients in the BCC field. Your mail program may not have the BCC field available by default. Here’s where you’d look from within Apple’s mail program.