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Email Open Tracking: Find the Hour Each Contact Reads

If your emails to people in other time zones keep getting buried, email open tracking gives you something better than a guess: the actual hour each recipient opened your last message. Take that timestamp, convert it to their local time, and schedule the next email a little before it. Gmail's built-in Schedule send handles the delivery; the tracker tells you which hour to aim for. The rest of this article shows exactly how to do that, where it goes wrong, and what you can do without a tracker at all.

Why "9 a.m. their time" is usually the wrong guess

Most send-time advice assumes everyone reads email first thing in the morning at their desk. In practice, the person you are emailing might be a contractor in Lisbon who checks mail at lunch, a client in Sydney who clears the inbox at 7 p.m. after the kids are asleep, or a professor in Chicago who only opens email on Tuesdays and Thursdays. "Their morning" is a rough guess, and it is often off by several hours.

Three things make the guess worse:

  • You do not actually know their time zone. A .de address can belong to someone living in Denver. A company headquartered in London may have the person you need sitting in Singapore.
  • Daylight saving time moves the gap. Today, 25 October 2026, is the day most of Europe sets clocks back. The United States does not change until 1 November. For the next week London and New York are four hours apart instead of five. If you calculated "their 9 a.m." last month, it is wrong this week.
  • Reading habits are personal. Two people in the same office, same time zone, can read email at completely different hours.

Open tracking replaces all three guesses with one piece of evidence: the time the recipient actually looked at your message.

Use email open tracking to see when they actually read

An email tracker inserts a tiny image into your outgoing message. When the recipient's mail app loads that image, the tracker records an open and a time. In Gmail you need an extension for this; personal Gmail accounts have no built-in read receipt, and Google Workspace read receipts only work when the recipient's organisation allows them.

For this job, you are not interested in whether someone opened. You want the when. One open gives you a clue; three or four emails to the same person give you a pattern.

What to look for:

  • A consistent hour. If a contact opened three separate emails between 13:00 and 14:00 your time, that is their reading window, whatever the clock says in their city.
  • A consistent day. Some people batch email. If every open is on a Monday, a Thursday send will wait until Monday.
  • The first open versus later opens. The first open after sending tells you when they check mail. A second open two days later usually means they came back to act on it.

Any Gmail tracker that shows a timestamp will do. Zestmail for Gmail is one option: it is a Chrome extension that shows whether and when recipients open your emails, and it filters out your own opens and common bot opens, which matters here because a bot "open" seconds after sending would otherwise pollute your timing data. The free plan covers up to 20 emails a day and adds a small "Sent with Zestmail" footer; the Pro plan is $9 a month or $69 a year with a 7-day free trial. The extension does not request permission to read your Gmail inbox.

Whichever tracker you use, treat the timestamp as your own local time unless the tool clearly says otherwise. You will convert it in the next step.

Step by step: from an open time to a scheduled send

Here is the full routine for one recipient. It takes a couple of minutes the first time and a few seconds afterwards.

1. Collect two or three open times

Open the sent emails to that person and note when each was first opened. Write them down in your own time, for example:

  • Email 1: opened Tue 06:40
  • Email 2: opened Thu 06:55
  • Email 3: opened Mon 07:10

Ignore opens that happened within a few seconds of sending; those are almost always a security scanner, not a human.

2. Confirm their time zone

You need the offset between you and them. Fastest reliable method: open one of their replies in Gmail, click the three-dot menu on the message and choose Show original. Look at the Date: header. It ends with an offset such as +0100 or -0700, which is the time zone their mail client was set to when they replied. That is better evidence than the country in their email address.

Then compare with your own offset. If you are at +0000 (London after this weekend's clock change) and they are at -0500 (New York until 1 November), they are five hours behind you. Check again after any DST change; the week either side of a change is where most mistakes happen.

3. Convert the opens to their local time

Using the example above with a five-hour gap, their opens were at roughly 01:40, 01:55 and 02:10 local time. That does not look like a desk worker. It looks like someone checking the phone late at night, or a tracker catching an automatic preload. Either way, it tells you a 9 a.m. send would sit unread for hours.

If the converted times instead land around 08:30–09:00 local, you have found a morning reader. Aim to land 15–30 minutes before the earliest open, so your email is near the top when they start.

4. Schedule the email in Gmail

  1. Write the email as normal.
  2. Click the small arrow next to the Send button and choose Schedule send.
  3. Pick Pick date & time rather than one of Gmail's suggestions, and enter the target hour in your own time zone. Gmail schedules in whatever time zone your computer is set to, so convert back from their local time to yours. For the morning reader five hours behind you, "08:30 their time" means 13:30 on your clock.
  4. Click Schedule send. The message moves to the Scheduled folder in the left sidebar, where you can open it and click Cancel send if you change your mind.

If you are sending the same message to a group spread across time zones, Gmail cannot stagger one draft. Make one draft per region (say, Europe, Americas, Asia-Pacific) and schedule each separately. Zestmail's scheduled sending and its mail merge from a Google Sheets URL can cut down the copy-and-paste if you do this regularly, but a few scheduled drafts in plain Gmail work fine for small lists.

5. Check the result and adjust

Look at when the scheduled email was opened. If the open now comes within an hour of delivery, you have the right window. If it still waits half a day, you have the wrong zone, the wrong day, or a reader whose habits changed. Adjust and try once more.

Free ways to find a reading window without a tracker

You do not need an extension to get most of the way there.

  • Reply times. Look at the timestamps on their past replies to you. People usually reply during the same window they read. Gmail shows these in your local time, so convert exactly as above.
  • The Date header. The Show original trick works on any message they have ever sent you and costs nothing.
  • Calendar invites. If you have ever had a meeting with them, the invite they accepted or proposed shows their working hours more honestly than their signature does.
  • Ask. "What time of day is easiest for you to go through email?" is a normal question, especially for a long-running project. Many people will tell you, and it skips all the guesswork.
  • Google Calendar's world clock. In Calendar settings, under World clock, add their city. You then see their current time next to your calendar every day, which makes DST shifts obvious.

A tracker adds value when you email many people you do not know well, or when replies are rare and you have no other signal. For a handful of regular contacts, the reply timestamps and one honest question are usually enough.

When open times will mislead you

Open tracking depends on an image loading, and several things interfere with that. Be realistic about what the timestamp can tell you.

  • Apple Mail Privacy Protection preloads images on Apple's servers, often shortly after delivery and regardless of whether the person has looked at the message. If a contact uses Apple Mail on iPhone or Mac, their "open" times are unreliable for this purpose. Fall back on reply times.
  • Image blocking. Some corporate mail systems and privacy-conscious readers never load images, so you see no open at all. No open is not "didn't read".
  • Security scanners. Opens that occur seconds after sending are typically a link or attachment scanner. Good trackers filter the common ones, but none catch everything.
  • Multiple devices. A phone glance at 06:30 and a proper desk read at 09:15 may both register. The first open shows when they saw it; the later one is closer to when they acted on it. For scheduling a message that needs action, the later window is the better target.
  • One-off behaviour. A single open at 23:00 might be an airport, a sick day or insomnia. Wait for a pattern before moving your send time.

Used with those limits in mind, open tracking turns "send it in their morning and hope" into "send it twenty minutes before the hour they reliably open mail". Combined with Gmail's Schedule send and a quick check of the Date header, that is a routine you can run for every important contact in a different part of the world.