If you send e-mail to multiple contacts at the same time we recommend following steps.
- Check your settings for e-mail addresses, you should not use addresses as bubbles now.
Preferences > General > Other
- Remove the check mark that are in the box in front of Show email addresses in bubbles > Save.
- Open the Address Book and choose the ones you want to send to. Select multiple contacts with Ctrl + click or Shift + click to select as a serie.
- Right-click one of the selected contacts > New e-mail message.
- Select all the contacts that have now fallen into the To box, right-click > Cut.
- Click Show Bcc and put the cursor in the Bcc box, right-click > Paste.
- Enter the e-mail address in the To box because some mail servers do not accept empty To field.