Quite some time ago, I needed to do a big cleanup of email aliases (I have 500+) and various My approach was to use IMAP integration with my provider to copy a

Quite some time ago, I needed to do a big cleanup of email aliases (I have 500+) and various My approach was to use IMAP integration with my provider to copy all the emails down to my laptop. I then used VBA in Outlook to create a list of source email addresses and counts - then I could update places using those emails. In your case, i'd do something similar. Analyse your existing emails to get a list of emails by source address (or domain). Use that list to figure out what places you need to get updated. Then (per Sydney1's suggestion) - forward old emails to the new address. Preferably tag it somehow so you know that it means there are other places that need to be updated.