I think that having email addresses are somewhat like paper mail addresses – they suggest whether the addressee is a private individual, or a representative of a business or institution.
If you a representative of an enterprise that has an internet domain name, it’s sensible and helpful for you to use that DN in your email address. If you are representing yourself as a private individual, I think it’s best to use a public domain, such as gmail.com.
Using a personal email domain when you don’t own the homepage of that domain can harm your reputation. When I see an email address with an unfamiliar DN, I often visit that domain with a web browser, to see something about the enterprise the addressee seems to be representing. If the homepage is a generic “your URL here” page, I’m inclined to believe the addressee is being deceptive, trying to give the impression of representing an enterprise when they are really representing only themself.
So I recommend not getting a personal email domain until you are ready to maintain a website at that domain. Even if you have a website, there are time still when it’s better to use a email address at a public domain.
On a related sidenote, I wish the various nations that include in their constitutions a state power (and thus, implicitly, an obligation) to provide paper mail service had, when the internet was young, had provided truly public email domains (and also proof-of-identity services), but that didn’t happen. This Bloomberg.com article
explores some of the history and reasons why.