Too often, I read email conversations that go back and forth many times. It is typically because the individuals communicating do not understand each other or they are having an indirect professional disagreement.
There are other cases where a team member mentions that they are having trouble getting a response from someone, often someone outside of our company.
In both of these cases, I ask my team members to talk to the other person over the phone.
People feel like they are too busy or prefer to send an email believing that it is the most effective way to communicate or get the task off their plate when it is not. In the examples above, it is a lack of understanding that causes these problems. Communication fidelity is important.
The fidelity hierarchy is, from high to low: in-person, by phone, and then by text.
When an email conversation is going back and forth too many times then you should talk to the person.
A final note, in most cases, you should not be writing long emails to your colleagues at work. These should also be conversations.