https://github.com/q2a/question2answer/blob/master/qa-include/app/mailing.php#L129
'body' => trim(qa_opt('mailing_body'))."\n\n\n".qa_lang('users/unsubscribe').' '.$unsubscribeurl, 'html' => false,
I would add a flag so we can use HTML too:
Furthermore I would use instead a plain URL: $unsubscribeurl a link so HTML can be used.
Seems that the $html flag would decide about the body unsubscribe link.
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.