Not sure what you mean by additional B tags, there is one in that message, it might work, it might not, you can add more and they might work or might not. I really depends on the client. Email is just text. It’s up to the client to decide how to display that text.
What mostly works is writing an actual HTML page in the body of the email, so if you did something like:
"""
<html>
<head>
[ Define CSS and whatever. ]
</head>
<body>
[ Enter the body of the message. ]
</body>
</html>
"""
One thing when writing HTML for email clients, you need to write it like it’s the 90s and use tables to do all your layout. Some email readers have never gotten with the times and fully embraced CSS.
You best bet is googling for “HTML email templates” and start with one of those and edit it for yourself.