This looks a lot like a direct clone of https://forwardemail.net/, except that ImprovMX isn't open source. I wonder which came first?
I like simplelogin.io (also open source, so can be selfhosted) because the aliases can be used to send and receive, though you do have to set the domain up on their platform first.
I can answer that easily (I'm the founder of ImprovMX).
Forwardemail was created well after us (ImprovMX goes back to 2013).
We are not Opensource, but that doesn't mean we track user's email (we don't, we wrote about it: https://improvmx.com/are-you-reading-my-emails/). On the contrary, screaming to anyone that one uses Opensource doesn't mean they respect user's privacy (like Forwardemail does): take their way of forwarding for instance: you need to add your email in the DNS settings, publicly available... they have a odd definition of privacy.
And don't get me started on their homepage full of misleading messages ... ;)
I like simplelogin.io (also open source, so can be selfhosted) because the aliases can be used to send and receive, though you do have to set the domain up on their platform first.