Thanks Jason, it's working now. I also discovered that the email address was held in double quotes "email@" in the database. So rather than use the 'to' field, I switched it to the 'account' field and got it working.
I am now trying to figure out how to ensure that the body of the email message does not get posted twice, as plain text and html, even though the original email was sent as html.
Another puzzling side effect is that the two php files I am testing with (calgary.php and newsletterarchives.php) are ignoring the css class for hyperlinks and rendering hyperlinks as plain blue underlined, whereas the css file has the class as grey underlined, which renders okay on all the other pages on the site.