So, my good friend, what we both know is that nobody can be "blocked from sending e-mails", as sender@somedomain can be used on SMTP from many ISPs and someone with the resources that Trump has can just buy one and I doubt Trump has "one" e-mail, and the message I am replying to says "one of the service providers to Trump's team has cut access".Yes, in theory you can host a website on your own computer. In theory.
I advise you to read up on this little thing called an "ISP", they tend to block/restrict SMTP unless it's from a hosting provider. And what do hosting providers do? Well, they kind of deplatform anyone if a rando on twitter complains enough.
As you say a website can be hosted on a single computer and I think maybe Trump has the resources to buy more than one computer in many different countries and even connect to a dial-up number on a satellite phone with Iridium or something so unless he is in handcuffs I think "Trump is blocked from sending e-mails" is unlikely, it's just boomers on their iPhones writing hello fellow internauts how are the cyberwebs