no worries brother. sendmail is an email utility that runs on your server. You can tell it to do whatever you want. (and there are many alternatives that do this too) Basically it sends whatever you want as an email.

Badges: When you send an email, you're sending to the recipient's email server--gmail.com or whitehouse.gov or whatever. But these servers get a billion spam messages a day, so you need to prove you're really boeing767.com, else most of your messages will get flagged as spam. This is typically done by adding SPIF and DKIM (special DNS records) for whatever domain you use, e.g. boeing767.com

Chatgpt can pretty much write the code do this this (or get you up to speed on how it all works) if you don't want to spend a bunch of time on it.