A long time ago I've maintained a C# version of Password Expiry reminders. It was working based on HTML templates and was quite painful to setup and make sure it's working as expected. Problem with password notifications and setting up something that whole company will potentially get is always risky. You don't want to send 500 emails to all users just because you want to test out if your HTML template is actually looking as you want it to. So when Client asked me to enable password notifications for him I've decided that it's time to start with something new. You can of course find a lot of possible options ranging from few lines scripts, to full blow software but I had few priorities of my own. I've made sure the code is published on GitHub (so you can give feedback / report issues there) but also it's published as a module on PowerShellGallery so highly deployable.
This is how the template for users look like. You can customize it to your needs. It's just an example I've done for testing purposes. You can pick your own links, colors, style and data you want to include in email. The looks is mostly up to you with fairly easy config file.
This is how the template looks for managers. Again it's configurable by you. The only thing that's a bit static is the table in the middle. You can cut out some of the fields from it via config file thou.
Finally this is how the email to admins looks like. There's no template here except for choosing amount of reports you want to get. My idea is that admins don't need formatting. They need data… so there it is..
If you like what you see feel free to visit the dedicated module page PSPasswordExpiryNotifications which contains all the know-how for it.