I'm using PHP Mailer since 1 year, embedded in a Dreamweaver Template. Everything was working perfectly in 8 Websites with different contactforms. Yesterday I saw, in IE Edge after sending, it shows only MF004 on a white page. In Firefox its working some times.
Its different sites with different PHP-Versions, 5.6 / 7.1 /7.2 with all Versions the same error and some days before everything was perfect. We didn't change anything at these websites in the last 3 weeks. I have no more idea.