I'm using a customized wordpress installation and the mails sent are not in html

That might be related to your Sending Method. https://support.mailpoet.com/knowledgebase/newsletters-are-sent-with-simple-text-version/

yes it is shown in text/plain in gmail.

i’ve narrowed down the problem to be this line: add_filter(‘phpmailer_init’,array($this,’wpmail_init’),90);

the issue is, i’m using wp_mail to send and no matter what i did to the next line,

$result = wp_mail(‘[email protected]’, ‘subject’, ‘BODY’, ‘example’);

it will always send the one from within the system. I think there’s something to do with the add_filter. how do i resolve this because I would like to be sent the html version. What’s the last function executed before the sending by wp_mail?