I think it's not fake leads, it's more they don't open it because they receive so many emails from others and your email get buried by them.
Another reason is, they use their dummy emails to opt-in to your mailing list.
And here's what to do if those situation above happen:
Set up followup emails that send daily after they opt-in.
About 7 days of followup emails is enough.
If you want more, that's fine as well.
In fact, I suggest you to create about 30+ followup emails.
Because sometimes, they just want to see if you only sending them emails to make money off of them or you send them emails because you want to build a relationship with them.
And that's why the purpose of sending daily email is to build a relationship with them and at the same time, to filter them as well.
What do I mean by filter them?
Well, to filter which one is the bad leads and which one is the good one.
If it's good, keep them.
If it's bad, delete them.
And you really have to delete the bad leads because if you don't, your emails is going to promotion tab or worse spam folder because of them.
I've tried GetResponse.
For the first few weeks, it's good.
After that, not so much.
Because my emails go to promotion tab using them.
So since then, I'm just using an email marketing platform called Kirim.Email.
It's cheap and can do the work for me.
The plus is, they are easy to use when it comes to broadcast an email. The reason why is because there are only 3 step to broadcast an email using them.
And their autoresponder?
It looks like ConvertKit.
And one more thing.
The minus using them is, they don't allow single opt-in.