Why not connect JIRA to an Active Directory instead ? I see a good time for you to make this change and administer user authentication centrally - and bulk changes are always possible via AD.
Or may be considering that you use internal directory - why not run a DB query to make the replacement of all user email addresses, just a thought, haven't done it myself.
Update: That's a wrap! Thanks so much for your questions. If you didn't make it for the live AMA, not to worry. Add your questions below and I will get to them ASAP. Hello Atlassian Community...
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