Send Time Optimization

Send Time Optimization

If you want to maximize your open rate you can try the new “Send Time Optimization” feature that allows you to send emails to subscribers based on their last open time. When sending a campaign, you can now enable a new 'send time optimization' option from Account settings > Features. Selecting this means your contacts' historical open behavior (over the last 90 days) will be automatically analyzed, timing emails to reach the subscriber’s inbox when they're most likely to be read. As a result, optimized campaigns can take up to 24 hours to finish sending.


You can opt to send a campaign using send time optimisation on the second step of the 'Select contacts and schedule campaign' screen. Choose "Optimised".


This will start sending your campaign immediately, but will optimize the time of individual sends to maximize open rates based on your contacts' historical behavior. This can benefit you by ensuring your sent emails are timed to reach inboxes when they're most likely to be read, increasing your open rates. 

Campaigns optimize over a period of 24 hours from when you send, and remain in the Outbox until complete.

Sending a time-optimized campaign:

Any campaign, with the exception of split test and triggered campaigns, can be time-optimized. In the 'Contacts' stage of the campaign creation process, select Optimized in section two. The campaign can then be sent as normal.

Compatibility with other features:

Some OpenMoves features won't be available when optimizing a campaign.

Compatible Features:


Time-optimised campaigns can be sent through the API. Users of the SOAP API can use SendTimeOptimisedCampaign. Users of the REST API can use Send time optimised campaign.

Pausing and cancelling

Time-optimized campaigns can be paused and cancelled. When an optimized campaign is in the process of sending, it will remain in the Outbox. From here, it can be paused or cancelled like any other campaign. 

When a paused time-optimized campaign is resumed, any sends that would have been sent during the paused period will be sent immediately. If an optimized campaign is paused for longer than the optimized period (anything up to 24 hours), all sends will go immediately when it is resumed. 


ReMail can be used with time-optimized campaigns. However, a minimum wait time of two days applies, rather than the normal one day for non-optimized campaigns. This is to leave a minimum of one day between the last optimized send and the start of the ReMail.

ReMail sends are always non-optimized, even if the original campaign was time-optimized.


Reporting does work with optimized campaigns. Reporting for optimized and non-optimized campaigns works in the same way. However, for optimized campaigns, the reporting overview will display 'Campaign type: Optimized'.

We recommend waiting for an optimized campaign to finish sending before using the reporting statistics, as these are subject to change while a campaign is still sending.

Not Compatible Features:

Scheduled campaigns

Scheduled campaigns cannot be time-optimized. A campaign can either be sent immediately, scheduled or optimized. When scheduling a campaign, you decide when it's sent. When optimizing a campaign, we decide when it should be sent.

Split testing

Split test campaigns, of any kind, cannot be time-optimized. When a split test campaign is sent, we immediately start sending the test versions to the sample group. This happens at the same time as any optimization would start. As a result, the two are not compatible.

Controlled (spread) send

Optimized campaigns cannot also be controlled (a spread send). However, optimized campaigns are 'self-throttling' - and are naturally spread over a period of up to 24 hours. Therefore, it is unnecessary to want to add extra control to an optimized campaign.

Triggered campaigns

Triggered campaigns cannot be time-optimized. The send time optimization setting comes after the last step of creating a triggered campaign, and so cannot be chosen.

How it works:

Send time optimization operates as follows:

  • We analyze the historical data for each contact individually. Therefore, an optimized campaign can consist of up to 24 separate send periods (i.e., we do not pick just one send time for the entire send, which would be less accurate).
  • We analyze a rolling period of the previous 90 days from hitting the send button. For regular or semi-regular senders, this generally gives us several historical engagements. This also allows the system to re-learn if a contact's behavior changes, for example if they move country (see also the notes on time zones).
  • We only analyze data belonging to the account that's used to make the send, i.e., if a contact's email address exists in multiple accounts, only the open behavior in the sending account will be used.
  • The 24 hour optimize period begins when the send button is clicked.
  • For contacts where no historical data is available (they're a new subscriber, for example), we'll send the campaign immediately.

Also note...

Time zones and sends to multiple countries

Send time optimization is deliberately time zone-agnostic. When an optimized campaign is sent, we'll deliver at the predicted best time to increase opens - regardless of where the contact is. 

This means that for sends to contacts in multiple time zones, time-optimized campaigns are strongly recommended.

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