Does anyone have any resources for HTML email in Japan or other locales?

We recently discovered some issues with Bulletproof email buttons (or rather, links in HTML in general).

The issue seems to affect anyone under the @docomo.ne.jp domain. Here are some documents (in Japanese) from Docomo that I was referenced by some Japanese contacts unfamiliar with HTML email. I can't understand any of it, but would love any translation or insight:
https://www.nttdocomo.co.jp/service/developer/smart_phone/make_contents/deco_mail/index.html
https://www.nttdocomo.co.jp/service/developer/make/content/deco_mail/mechanism/
https://www.nttdocomo.co.jp/service/developer/make/content/deco_mail/tag/