That's a spam email. It's also a red herring, because your priority needs to be your reaction to these things whether they are authentic or spam.
You need to book an urgent GP appointment and tell them how fragile your mental health is at the moment.
And if him using porn is a dealbreaker for you and means you cannot possibly have a healthy relationship, then you need to communicate that to him and if you find out he's been using porn you need to own that dealbreaker and end it.
You can't control and manipulate someone into 'obeying' your rules. I know you don't feel like you're abusing / controlling / manipulating him and that you don't mean to do so, but getting to the point where your mental health is so fragile he hasn't been able to tell you he works with a woman is absolutely shocking. I'm not saying he was right to lie but it sounds like he was backed into a corner.
You would never have been happy about him working closely with a female colleague and would have quizzed him about it relentlessly whenever you found out so I don't blame him for not telling you. It's work and he works with the colleagues who do the appropriate job, whether they are male or female.
I'm trying to be gentle with you while also explaining how far out of the norm this behaviour is because I really think you need to seek some help.
You're spiralling and having intrusive thoughts. That's serious and you deserve support but your husband is not suitably qualified to do the job of a mental health professional and he can't fix this problem. He can support you as a partner, but you need external support quickly 