Definition

Open rate is the share of delivered emails that were opened. If an email reaches ninety inboxes and thirty of those people open it, the open rate is one in three.

It is counted with a tiny tracking image that loads when the email is displayed. That makes it a rough signal, not a precise count. Some email clients load the image automatically, which counts as an open even when nobody read anything. Others block it, so real opens go uncounted. Open rate is not a measure of whether people found the email useful; it mostly reflects the subject line, the sender name and the time of sending.

A B2B example: a marketing lead tests two subject lines for the same newsletter issue and sees one opened far more often. That tells them which framing got attention, not which issue was better.

Why it matters for B2B email

Open rate is still the quickest read on whether your subject lines and sender name are earning attention from a B2B list. Watch the trend over months rather than any single number, and pair it with click rate and replies, which say more about whether the content actually landed. A sudden drop is also an early warning that deliverability has slipped.

Related terms

Click rate Click rate is the share of delivered emails where someone clicked at least one link.
Click-to-open rate Click-to-open rate is the share of people who opened an email and then clicked a link inside it.
Subject line A subject line is the short line of text that shows in the inbox before an email is opened.
Deliverability Deliverability is whether your emails actually land in the inbox, rather than in spam or nowhere at all.

Part of the B2B email marketing glossary. Last updated 2026-10-08.