I just want to post some screenshots of an email in a video to give my story context. I will use fake names for everyone and remove any personal information so everyone is anonymous. If the sender sees the video are they able to take legal action?
It may be legal to publish the sender's text. The risk is a copyright infringement suit, but you might be able to avail yourself of the fair use defense since you are "commenting" on the work. Your use seems to be "transformative", not just copying and redistributing, but creating something now where the original – in a modified form – is a component of something else. The court would be concerned with whether your copying had affected the market for his work. It's most likely that a fair use defense would prevail, unless there are important details missing. You might get sued for public disclosure of private facts, if a reasonable person would find it objectionable to disclose the fact, but we have no idea what kind of facts are disclosed. Anonymization doesn't necessarily protect you. The question is whether the subject of the disclosure is identifiable.