https://confluence.atlassian.com/display/AOD/Creating+Issues+and+Comments+from+Email is a good startting place.
Hypothetically you could create a email address and then route it to Atlassian after you've worked with them to meet any needs they require. They may have additional addresses that you can purchase.
It's more the whole "worked with them to meet any needs they require" thing that I can't figure out. I've set up plenty of email handlers for Jira before, but I can't find a single reference to how to ask Atlassian for another address or what addresses other than jira@<domain>.atlassian.net are available.
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