It’s actually a good question and you’re getting a lot of shit for it from people who seem to not even know where this accusation comes from.

https://tuta.com/blog/tutanota-not-a-honeypot

“So, I was briefed on a storefront that was being created or had been created in order to attract targets – criminal targets to this online encrypted service that was being created, in order for them to – the criminals or the targets to use this service in order for intelligence to be collected by the agency that created the storefront. … It’s an online end-to-end encryption service called Tutanota.”

It can be a lie, a mistake, or truth. It can even be a false flag accusation to destroy their reputation. We don’t really know.

When looking into this it’s good to also know about Tor Mail: https://en.wikipedia.org/wiki/Tor_Mail
There might have been some confusion between Tutanota and Tor Mail.

I don’t think anybody here will be able to actually answer it.