Say you're the chair for a bar association program, so you're sending out personalized email invitations to your fellow members. However, your assistant is handling the RSVPs. How do you send your email so that (a) your assistant gets the RSVPs (not you) and (b) recipients don't accidentally reply to the entire list and cause everyone's inbox to melt down?
Solve the RSVP problem
Not many Microsoft Outlook users know this, but it is possible to specify a different "reply to" address than your own. This little trick is under Options within the New Email window for all versions:
Solve the "reply to all" problem
Caveat: Outlook's really not a good choice for sending out mass emails, because emails with more than a few recipients tend to get caught in spam filters unless you're using email marketing software/services like AWeber, MailChimp, Active Campaign or Drip.
But if Outlook's all you've got, then make the most of it. If you're using a version of Outlook prior to Office 265 (e.g., 2010 or 2013), you can install a plugin or use one of several techniques depending on your tech savvy. In versions 2016 and 2019, you can build your own custom mail form that disables the Reply to All function.
Remember: people don't read carefully, particularly online, so your "if you're interested, please email my assistant at ..." instruction will probably go unheeded. Use the above techniques to make sure that, even if they don't follow instructions, they reply to the right person anyway!