You shouldn't reply to emails, now they have your IP address and know where you live.
When people are brought into productions they are usually contacted by their manager or agent, that is the professional way things are done.
Even with independent films and internet TV series.
Often with featured films and TV you have to be SAG or SAG eligible to participate with a certain number of lines, speaking roles. It's all very unionized. They don't hire non-sag people, even the people you see on tv shows that talk in the audience, or are "randomly selected" from the audience are hired professional actors.
Whoever did this was likely trying to scam information out of you.
Anything that is a financial production, is produced. Things are approved ahead of time. But yeah it's unprofessional to contact people directly this way as well, it should always be done through an agent or manager, because it creates legal problems... especially with non-union people.
They do hire "randoms" *sometimes* they do casting calls, like on the streets of New Orleans they opened up casting once to "everyone" and anyone off the street could come to this location, and audition. Sometimes Universities with student films will do this too.
But if you didn't audition, this is kind of sketchy if the person who recruited you, you didn't ever meet in person... you aren't an actor, and you haven't submitted any audition tapes in your life.
edit: you should be careful even opening things. on facebook messenger, via text, emails, phone calls. i just don't ever feed into it.
once, my parents picked up an anonymous call, and it was scammers trying to threaten them with their childrens lives if they didn't fork over 50grand. Yeah, that actually happened. The police were called, it was a big ordeal. Trust few, especially those trying to offer you something.