Reference your prior communications
Your previous emails to a prospect may still be fresh in your mind, but you shouldn't assume that the prospect is equally focused on the exchange, or that they've even seen your prior emails at all.
Source: Sales consultant Heather R. Morgan
Open your follow-up email with contextual information that reminds the recipient who you are and what you've previously discussed. Casually mention specific details about prior progress, to avoid redundancies and keep the conversation moving forward.