Drupal - How to send HTML email

You can pass Spanned text in your extra. To ensure that the intent resolves only to activities that handle email (e.g. Gmail and Email apps), you can use ACTION_SENDTO with a Uri beginning with the mailto scheme. This will also work if you don't know the recipient beforehand:

final Intent shareIntent = new Intent(Intent.ACTION_SENDTO, Uri.parse("mailto:"));
shareIntent.putExtra(Intent.EXTRA_SUBJECT, "The Subject");
shareIntent.putExtra(
Intent.EXTRA_TEXT,
Html.fromHtml(new StringBuilder()
    .append("<p><b>Some Content</b></p>")
    .append("<small><p>More content</p></small>")
    .toString())
);

Been trying to send html via gmail app for a while, so decided to leave some insight on what I found, just in case someone else is having similar issues.

Seems like no matter what I did, I couldn't get the html to have bold text in it. Then I've tried switching to outlook client and to my surprise it was working just fine. Html markup was also working on other older devices, but not on mine (galaxy s7 API 26), so I figured, that gmail app seems to have dropped support for html syntax that comes from intent or maybe now you're required to provide it in some very specific way which is not clearly documented.

Last gmail version that worked for me was version 6.9.25... on Nexus 5X API 25 emulator (Nougat) And it stopped working starting version 7.5.21... On Nexus 5x API 26 emulator (Oreo)