Here’s the Lowdown: When you receive a bounce-back email with the error #550 5.1.1 RESOLVER.ADR.ExRecipNotFound, try clearing cached entries from your Nickname list or deleting your Nickname Cache file.
If you are having problems with a single recipient, you can delete the individual cached entry.
To Delete a Single Cached Entry
- Open a New Message window in your Outlook account.
- From the File menu, select New- Mail Message.
- Type one or more letters of the recipient’s name or email address. The cached entries automatically display in the Email list.
- Select the entry you want to delete with your arrow keys, and then press the DELETE key on your keyboard.
NOTE: The entry is removed from your Auto-completion Cache.
If you are having problems with multiple recipients, you can delete your Nickname Cache file.
To Delete the Cache File in Microsoft Windows XP
- (Optional) Exit the Outlook program.
- Start Microsoft Windows Explorer.
- From the Tools menu, click Folder Options.
- Go to the View tab, and from the Advanced Settings menu select Show Hidden Files and Folders, and then click OK.
- Click Start, select Search, and then click All Files or Folders.
- In the Search Companion area, type .NK2 in the File Name field.
- From the Look area, select your local hard drive, and then click Search.
- Right-click the .NK2 file for which you want to reset the name, and then click Rename.
- In the File Name field, type profile name.bak, and then click Enter.
- Exit Windows Explorer, and restart Outlook.
To Delete the Cache File in Microsoft Windows Vista
- (Optional) Exit Outlook.
- From your the Start menu, select Search.
- Click Advanced Search.
- Select Include Non-Indexed, Hidden, and System Files.
- In the Name field, type .NK2.
- Delete .NK2, and then restart Outlook.
NOTE: As a courtesy, we provide information about how to use certain third-party products, but we do not endorse or directly support third-party products and we are not responsible for the functions or reliability of such products. Outlook® is a registered trademark of Microsoft Corporation in the United States and/or other countries. All rights reserved.