Cannot be done natively through Facebook.
Your only hope is to be able to export your Facebook contacts and run them through a mail merge on your local.
Or try and upload/import the contacts list to Gmail and use Google Docs as a way to send out personalised mass emails.
If you wanted to try your hand at the Gmail & Google Docs method, "Create a Mail Merge with Gmail and Google Docs" has some steps. They are roughly thus:
- Create a new Google Docs Spreadsheet
- Select "Mail Merge" from the menu and allow authorisation access to Gmail and/or Google Contacts
- Create a new group on Google Contacts with the emails and details of those you want to send to
- Click Mail Merge → Import Google Contacts and select the name of the new group. The details should import.
- Compose the email as desired
- Go to the Mail Merge menu and click Start Mail Merge. The sending will begin and update.
There's a little more nuance in the link mentioned, but listed here is the general step direction you'll be taking.