Email requests setting doesn't accept hyphen(dash) '-' in email address for Cloud

Summary

• Cannot create a cloud mailbox in a service desk project if the name contains dash "-"
  
• The following error is reported:

   Invalid email address. Use letters, numbers, periods and underscores.
  

How to Replicate

1. Navigate to any service desk project on your test instance > Project Settings > Email request 
2. For Cloud email address click on edit to update the mailbox email address
3. Mention an email containing a hyphen (dash)

Investigation Done

• Do not see any error reported in Splunk logs
•  Following error is reported in the Developer console

  {"success":true,"validationErrors":null,"message":null,"code":0}
  

• The following bug was raised a long time ago: https://jira.atlassian.com/browse/JSDCLOUD-5092 and its related internal ticket "https://hello.atlassian.net/browse/HPT-4517?oldIssueView=true"
  which says that it was because our mailstore uses regex to validate the email address and that the underscore and dash are now included. However, the ticket is very old.
• Raised a request https://hello.atlassian.net/browse/MSG-332 and they responded follows:

  yesterday

  We no longer validate the mailbox name in Vertimail (the incoming email service). We only validate the domain name.

  The error you’re describing sounds like Jira doing validation on the local-part (mailbox name). This is completely self-contained within Jira these days so you’ll need to speak to the Jira Cloud team.

• Further the regex currently used to validate e-mail address still seems to treat hyphen as invalid.

                  if (alias.match(/[^\w.]/)) {
                      this._showErrorMessage({
                          errors: [{errorMessage: AJS.I18n.getText("sd.email.invalid.email.address")}]
                      });

  
  Underscores are however accepted.

Workaround

None available at present.