Q: Envelopes feeding through but not printing.

Howdy debsdancer,

If you still haven't been able to print envelopes successfully from your Contacts app, I would use the troubleshooting in the following article to help you out here:

Troubleshooting printer issues in OS X

1. Use Software Update to find and install the latest available updates. If an update is installed, see if the issue persists.
2. Open the Print & Scan pane or Print & Fax (Snow Leopard) pane in System Preferences.
3. Delete the affected printer, then add the printer again.

If the issue persists, try these additional steps:

 

1. Reset the printing system, then add the printer again.
2. If the issue still persists, reset the printing system again.  Download and install your printer's drivers. Then, add the printer again.
3. Contact the printer vendor or visit their website for further assistance.

Thank you for using Apple Support Communities.

All the very best,

Sterling

No problem!