Email open rate

When the recipient's mail app loads it, the sender logs an open. Unique open rate counts each recipient once; total opens count every load. Delivered means sent minus bounces. Mailchimp defines open rate as the share of successfully delivered emails that recipients opened.

Apple announced Mail Privacy Protection in June 2021. In Apple Mail it downloads remote content, tracking pixels included, in the background whether or not the person engages with the email, so senders record opens that never happened. Mailchimp warns that bot activity, including Apple's, can falsely inflate open and click metrics. The result: open rates run high and swing with your audience's mail apps.

For example, a campaign sends 2,000 emails and 40 bounce, so 1,960 are delivered. The pixel records 1,100 unique opens, a 56% open rate. But 700 of the recipients use Apple Mail with privacy protection, so many of those opens are automatic. The 52 replies, 2.7% of delivered emails, are the number to trust.

Many cold email teams turn open tracking off and measure what people do instead: reply rate, positive reply rate and meetings booked. If you keep opens, use them only as a relative check. A sudden drop across every campaign at once can point to a deliverability problem worth investigating.