Form Plugin for Craft CMS I'm looking for a plugin like ContactForm from P&amp;T but with more options like validation for custom fields or the possibility to build a own mail template for the mail at his self.

I want to handle all with the same plugin if this is possible.
You can find most plugins for Craft here: https://straightupcraft.com/craft-plugins

There's a few different form plugins to choose from, not sure if all of them will have what you're looking for.

I've used Sprout Forms a few times and you should be able to do both of what you're asking for.