This will only occur if the user that sends the mass email has their Locale set to Spanish (ex: Spanish/Mexico).

We are currently evaluating this issue and will update the article when we have more information.

To prevent this, you can first change the Locale of your user account to English (ex: English/United States) prior to sending the mass email. This will convert the standard Opt Out link back to English, but the rest of the email will remain in Spanish (assuming the content of the email was originally written in Spanish):
  1. Click Home in the menu
  2. Click Manage User Preferences
  3. Set the Locale drop down menu to English/United States
  4. Click Save And Edit
  5. Log out of eTapestry, then log back in
  6. Send the mass email