Works for me. I open MaxBulk Mailer 8.5.1, I paste your code, set the message format to 'Styled Text' and switch to the Preview panel. The link is there, is clickable and bring me to the right place when clicking on it.
Have you installed MLM at some point? If so, is the MLM URL a valid URL? You can check that in the MaxBulk Mailer preferences, second panel.