Theres's nothing stopping you from having a JID username@example.com and an email username@example.com. XMPP and e-mail are different protocols that operate on different ports, so their respective clients will figure out how to send a message to the correct server.

Now, if you're asking how you can set something like this up, then you independently have to set up an XMPP server and an email server on the same domain. Or use some kind of email to XMPP bridge.

In the same way in which you could use your phone number as your username on your computer. Although it's more convenient for XMPP ID and emailaddress to be the same.

Maybe this list is a start: https://en.wikipedia.org/wiki/Comparison_of_webmail_providers

But like another poster said, you don't have to put those 2 eggs (mailing and instant messaging) in the same basket:

• email and XMPP are distinct things
• you can absolutely have a mail provider AND a XMPP provider that are different entities
• that doesn't preclude using the same domain name for both services (this is a matter of DNS configuration and usages will be routed to the correct provider)

Essentially, what you need is:

• to register a domain with the registrar of your choice (and get a domain like matkalandar.tld)
• reach-out to a mail provider that lets you use your own domain name (google apps, mailbox, zoho, …) → they will service  your emails such as xyz@matkalandar.tld
• reach-out to a XMPP provider that lets you use your own domain name (conversations.im, snikket, …) → they will service  your chats such as xyz@matkalandar.tld

accounts, passwords, user accesses and management… will be different because effectively hosted by distinct service providers.

https://disroot.org/

Mailbox.org also does it, but their Ejabberd server is currently very outdated, so I really can't recommend them for the Jabber part.

There are probably some more, but this combination is sadly not anywhere near as popular as it used to be. The main problem is that hosting email is such a shitshow, so very few people that host a XMPP server want to deal with that.