Broken html email?

I've never used mailtrap. The solution, at least in my case, was simple once diagnosed. It's seemingly an issue with PHP's (v5.6 I think) implementation of quoted_printable_encode(), assuming that my code was hitting the condition at system/libraries/Email.php:1516

I haven't dug deeper as it's fixed for now, at least for me.

PHP Code:

...
1512        // RFC 2045 specifies CRLF as "\r\n".
1513        // However, many developers choose to override that and violate
1514        // the RFC rules due to (apparently) a bug in MS Exchange,
1515        // which only works with "\n".
1516        if ($this->crlf === "\r\n")
1517        {
1518            return quoted_printable_encode($str);
1519        }
...