Send emails when they’re most likely to be seen

Timing matters. With Mailzzy’s Send Time Optimization (STO), your emails are delivered when each contact is most likely to open and engage—automatically. No guesswork, just smart, data-driven timing.

Smarter delivery for smarter results

STO analyzes historical email activity to determine optimal send times for every contact. Whether you’re sending to individuals, groups, or large segments, you can ensure every email lands at just the right moment.

How It Works

Deep Engagement Analysis

STO examines 30+ days of contact-level open and click behavior.

Optimal Send Time Calculation

Identifies the best day and time for maximum engagement.

Day-Wise Timing Adaptation

Adjusts send times throughout the week for consistent results.

Flexible STO Application Modes

Apply STO by group, individual contact, or combined groups.

Applications & Examples

Weekly Newsletter

Use Group-wise STO to send newsletters to a subscriber segment when they’re most likely to check their inbox.

Launch Announcements

Use Combined Group-wise STO for a large campaign that needs to reach multiple groups at a time they’ll notice.

Follow-up Campaigns

Use Individual Contact-wise STO to send reminders or follow-ups tailored to each contact’s best open window, increasing the chance of response.

Everything You Need to Know About Timing Your Emails

Want to boost open rates with better timing? See how STO can help—your questions answered here.

What is Send Time Optimization (STO)?

It’s a feature that automatically schedules your emails to be sent when each contact is most likely to engage, based on past behavior.

How does STO determine the best time?

STO uses at least 30 days of email interaction data (like open time) to calculate personalized send times for each contact or group.

What are the different modes available?

That’s up to you. Based on your selected settings:

Group-wise STO: Best time for one group.

Individual Contact-wise STO: Custom time for each contact.

Combined Group-wise STO: Optimized time for multiple groups together.

Is STO’s calculation unique for each scheduled day?

Yes, STO uses historic day-wise user behaviour to recommend send times. When you schedule a campaign for a specific day, it pulls data for that day and suggests the optimal time based on past engagement patterns.