When mailing tabs, any open tabs which have HTTPS URLs are not included in the email.
This occurs whether "Include page titles" is checked or not.
It does appear that including HTTPS tab content is possible, as other "mail open tabs" extensions include them, such as http://www.macosxtips.co.uk/extensions/
Is it possible to save the page-titles of the tabs together with the urls? At least in those cases where developers have thought of meaningful titles theese would not have to be manually added in the email.