eAnnouncer is an interesting plugin to add to the MS Outlook which allows you to send emails to the recipient list, but personalizing each one, so that they are a bit more personal and not all the users of that list receive the same and typical email standard.
eAnnouncer also allows you to write both plain text (TXT) and HTML, as well as being able to attach any type of file.
You can also set the time delay that you want between each of the emails that are being sent to each of the users on the list. This way they will not all arrive at the same time.
You can free download eAnnouncer 32, 64 bit and safe install the latest trial or new full version for Windows 10 from the official site.