Yes, you "allow list" your sending address on your Amazon Device page for a Kindle, where you can copy or edit the Kindle destination address.
There is no email on the Kindle. It's the famed "Whispernet" delivery only from Amazon direct on WiFi or mobile/cell depending on model.
If you normally use a desktop email client that has SMTP settings (outgoing or sending server) then that's what you use in Calibre.
You can test send an epub from the desktop email
Here is ficticious hosting someone uses. But if you have email with your ISP, using their SMTP, it goes in the boxes.
The GMX & Outlook are only convenience. As indeed is the built-in email sending.
You are really sending from the ISP or mail provider or hosting company SMTP.
Many ISPs in UK and Ireland will block a personal SMTP, like is built into Calibre. So really for sending email to anything (rather than web mail) you need an SMTP on the internet that you hyave an account with. It can gmx or outlook, or your ISP or a hosting package.
I've tested "Send to Kindle" email, but not the newer web interface which allows bigger files. Your ISP or hosting may have a smaller SMTP limit than Amazon anyway.
I prefer to do my own conversions, use USB cable and keep my content private.
One could use the Calibre Share by Email to send PD (or your own created content) to friends, family or beta readers, but I prefer a specific written email with an attachment.
Other people could add your sending email address to their kindle, and then you can email PD ebooks to someone that has no PC or can't work attachments and USB.
One advantage of Kindle over all others, someone could have 3G/4G kindle you set up, and no Internet and you buy their books (on account you created for them) and also send them PD books.