DKIM\SPF Validation Fails for Domains That Start With a Numeral

Summary

When attempting to configure Jira Cloud to send mail on behalf of a custom domain, if the domain entered into domain-check.atlassian.com starts with a numeral the check will fail and a HTTP 422 (Unprocessable Entity) error will be returned in the browser dev console. In addition, if you attempt to configure a custom project e-mail address in JIRA using a claimed domain that begins with a numeral this will also fail and return an error stating 'DKIM/SPF validation error.' This occurs despite the SPF and DKIM DNS configuration being correct.

Environment

Jira Cloud

Steps to Reproduce

1. Go to https://domain-check.atlassian.com
2. Enter a domain that starts with a numeral (ex. 2wire.com, 99perblems.com)
3. Click 'Check' button

Or attempt to configure a custom project e-mail using a claimed domain that start with a numeral

1. Choose the Jira icon ( ,  ,  ,   or  ) > Projects.
2. Select Settings > Summary.
3. Under the Notifications section and click the pencil icon to the right of the Email address.
4. In the resulting Project Email Address dialog box, enter a valid email address in the Email field, and click Update.

Expected Results

SPF\DKIM records are verified or found to be missing
The project e-mail is set successfully.

Actual Results

'Unknown server error' is displayed.
Checking the browser dev console, a HTTP 422 error is returned.

Failed to load resource: the server responded with a status of 422 ()
 index.js:83 Error: Request failed with status code 422
 at e.exports (createError.js:15)
 at e.exports (settle.js:18)
 at XMLHttpRequest.d.(/anonymous function) (https://domain-check.atlassian.com/static/js/main.748193d6.js:4:8199)\{code}

 Attempting to set the project e-mail results in 'DKIM/SPF validation error.'

Workaround

None