Send Time Optimization in Oracle Eloqua

How Send Time Optimization works

Send Time Optimization uses each contact’s history of email opens to learn when they usually read email then sends them the email within the hour around that time. Someone who tends to open on Wednesday evenings gets the email on Wednesday evening and someone who opens first thing on Monday gets it then. Eloqua stores opens and clicks from email scanning tools and Apple Mail Privacy Protection separately from a person’s own engagement.

A contact with no open history yet is sent the email straight away and later sends adjust as their history builds. You can see what the model has learned on the contact record: the Most Engaged Time tab, a panel in the Redwood experience, shows the contact’s top three weekday and time combinations in the time zone of whoever is viewing the record.

STO is an Advanced Intelligence feature like Fatigue Analysis. Since June 12, 2025 it has been available to every Eloqua customer but it isn’t on by default: open a service request with Oracle Support to turn it on.

Turning it on for an email

STO is set for each email in campaign canvas emails, simple email campaigns and A/B test campaigns:

1. On the campaign canvas double-click the Email element.
2. Open the Scheduling tab.
3. In the Mode drop-down choose Enable Send Time Optimization.
4. Choose how to optimize: by time of day or by time of day and day of week.

An optimized email shows an STO icon on the canvas. Oracle notes that you don’t need to break an optimized send into smaller batches because STO already spreads it across time slots. To see whether it is paying off, the Email Analysis dashboard includes a Send Time Optimization performance chart.

Time of day or day of week

The two options differ in how long Eloqua may hold the email.

• Optimize by time of day sends at the contact’s best hour within 24 hours of the email step. The email goes out the same day or the next.
• Optimize by time of day and day of week picks the best combination of hour and weekday within the next 7 days. An email that reaches the step on a Monday can go out the following Sunday.

Oracle describes STO as suited to batch campaigns and not to time-sensitive email such as webinar and event invitations where a contact’s best time could fall after the event or too close to a registration deadline.

Day of week suits email that reads the same whenever it arrives, such as a newsletter or a nurture email. Anything with a date in it is safer on time of day or without STO at all.

What a delayed send does to a frequency cap

Every frequency cap built natively in Eloqua works by checking what a contact has already been sent. A shared filter of recent sends, a throttle field or a suppression list is checked by a decision step before each email. STO puts time between that check and the send. While the email waits it hasn’t been sent so no other campaign’s check can see it.

Take a cap of three emails a week and a contact who has had one email in the last seven days:

1. Monday. The newsletter’s decision step counts one email and lets the contact through. Day-of-week optimization holds the newsletter until Thursday.
2. Tuesday. A webinar invitation’s check also counts one email so it sends. That makes two.
3. Wednesday. A product update’s check counts two so it sends. That makes three.
4. Thursday. The newsletter goes out. The contact has had four emails in a week under a cap of three.

Each check was right about what had been sent at the moment it ran. Time-of-day optimization opens the same gap for up to a day instead of up to a week and on a heavy day that is enough for several campaigns to pass their checks before the first optimized email has gone.

Other settings open the same gap. A sending window (Only send during certain days and hours) holds contacts who reach the email step outside it and breaking a send into smaller batches over several days spreads one email across those days. Any of them delays the send after the check has run.

Using STO with a native cap

If your caps are built natively, three things keep the gap small.

• Check right before the email. Put the decision step directly in front of the email step, never in front of a wait step.
• Prefer time of day in capped campaigns. Keep day-of-week optimization for low-volume sends where an extra email now and then does little harm.
• Mark the contact when the email is scheduled, not when it sends. If you use a throttle field, set it in an update step just before the email step rather than after it. Other campaigns then see the contact as emailed from the moment the email is queued, which closes most of the gap STO opens.

None of this closes the gap completely. A native cap still depends on every campaign having the check and campaigns that check the same contact at the same moment can still all pass.

Send Time Optimization with the Email Governor

The Email Governor counts an email when it releases the contact to the email step, not when the email finally sends. Every governed campaign draws on that count straight away so the gap that lets optimized emails slip past a native cap doesn’t open.

The delay itself still matters though. With time-of-day optimization the email goes out within a day of being counted, which rarely matters for a weekly limit so the two work well together. Day-of-week optimization can hold the contact in the email step for days, long enough for an email counted in one week to arrive alongside the next week’s and for the contact to be sent more email than the cap allows. So in governed campaigns use time-of-day optimization only.

The Email Governor also mirrors your deliverability scheduling configuration so governed campaigns can keep using deliverability scheduling alongside your caps.