I've answered my own question. You export to Excel, do a find and replace and import the modified list to a new folder. Details below... Any thoughts? 1. In outlook, go to "File", then "Import and Export" 2. Choose "Export to a file", then click "Next" 3. Choose "Comma Separated Values (DOS)", then click "Next" 4. Select your contact list, click "Next" 5. Save exported file as "Contacts csv" to Desktop 6. Open the new file "Contacts MLXjet.csv" from the Desktop 7. Go to "Edit", then "Find", then "Replace" 8. In "Find what", type ".addbranding.com" 9. Click "Replace with", type ".mlxjet.com" 10. Then "replace all" Simply repeat steps 7-10 for any other extensions you wish to change. For example, to change .com extensions, you would replace ".com" with ".com.mlxjet.com", ".net" with ".net.mlxjet.com", ".org" with ".org.mlxjet.com" etc. 11. Close "Find and replace" 12. Save as "Contacts MLXjet" 13. A warning box will show up, "Contacts MLXjet.csv may contain features...." Click "Yes". 14. Close Excel 15. Go back to Outlook and Contacts. Go to "File", then "New", "Folder" 16. In "Create new folder" type in "Contacts MLXJET" 17. Go to "File", then "Import & Export", "Import from another file" 16. Select "Comma Separated Values (Dos), click "next" 17. Import "Contacts MLXjet.csv" from your desktop. 18. Click "allow duplicates to be created" 19. Save to the new folder you created in Outlook. 20. Open a new email. Click "To", and in the "Select Names" box at the top right, "Show names from the".....look for "Contacts MLXJET". All email addresses in that folder should be changed to include the new .mlxjet.com extension.