[1vuio0pswjnm7]

IMHO, there are two components to "email" that do not necessarily need to be connected

1. receving mail

2. sending mail

Only #2 became difficult

Internet subscribers receive lots of email to which they never reply

Sometimes "throwaway" disposable email addresses are useful^1

Various third parties offer this as a "service", i.e., #1 is disconnected from #2

Self-hosting #1 can provide an alternative to using third parties

Generally, the only cost is a domain name registration

1. Also HN commenters have complained in the past that email sent via self-hosted SMTP to certain recipients, e.g., Gmail recpients, may end up stored on certain undesirable third party servers. This is because the recpient uses a third party for both #1 and #2, a so-called "email provider"

[1vuio0pswjnm7]

When "throwaway" addresses are used this is sometimes to manage receipt of unsolicted commercial email ("SPAM")

But this is not the only purpose for which these disposble addresses may be used

[man8alexd]

You missed filtering spam in #1.