Use send time optimisation

Ensure your email sends are timed to reach inboxes when they're most likely to be read.

Gareth Burroughes avatar
Written by Gareth Burroughes
Updated over a week ago

You can choose to send a campaign using send-time optimisation on the second step of the Select contacts and schedule campaign screen.


When sending an optimised campaign, you can either send it immediately or schedule it for later.

  • Immediately
    Starts sending your campaign straightaway, but optimises the time of individual sends to maximise engagement based on your contacts' historical engagement.

  • Scheduled start
    Starts sending your campaign at the scheduled date and time; however, it also optimises the time of individual sends to maximise engagement based on your contacts' historical engagement behaviour.

Optimisation period

Campaigns optimise over a period of 24 hours from when your email is sent, and remains in the outbox until complete.

Send a time-optimised campaign

Any campaign, with the exception of split test and triggered campaigns, can be time-optimised. In the Contacts stage of the campaign creation process, select Optimised in section two. The campaign sending process can then be completed as normal.

Compatibility with other features

Some of the app's other features won't be available when time-optimising a campaign. Below, we run through what you can and can't use when using send time optimisation.



Time-optimised campaigns can be sent through the API.

External dynamic content

External dynamic content can be used in time-optimised campaigns. However, please be aware that each external dynamic content block performs an HTTP request, which can generally be slow to make. If you have a lot of external dynamic content blocks in your campaign then this could significantly reduce its send speed, which could cause delays with send time optimisation.

Pausing and cancelling

Time-optimised campaigns can be paused and cancelled. When an optimised 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-optimised campaign is resumed, any sends that would have been sent during the paused period will be sent immediately. If an optimised campaign is paused for longer than the optimised period (anything up to 24 hours), all sends will go immediately when it's resumed.


ReMail can be used with time-optimised campaigns. The minimum wait time is one day after the send is complete. This is the same wait time as it is for a non-optimised campaign.

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


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

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

A note on sending times

An optimised campaign report shows the time that Send campaign was pressed. It doesn't show individual sent times for contacts (which can be any time from the pressing of the button to 24 hours later).

Not compatible

Split testing

Split test campaigns, of any kind, can't be time-optimised. 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 optimisation would start. As a result, the two are not compatible.

Controlled (spread) send

Optimised campaigns also can't be controlled (using a spread send). However, optimised campaigns are 'self-throttling' - and are naturally spread over a period of up to 24 hours. Therefore, it's unnecessary to add any extra control to an optimised campaign.

Triggered email campaigns

Triggered campaigns can't be time-optimised.

How it works

Send time optimisation operates as follows:

  • We analyse the historical data for each contact individually. Therefore, an optimised campaign can consist of up to 24 separate send periods (i.e., we don't pick just one send time for the entire send, which would be less accurate).

  • We analyse 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 behaviour changes, for example, if they move country (see also the notes on time zones).

  • We only analyse 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 engagement in the sending account will be used.

  • The 24 hour optimise period begins when the send button is selected.

  • For contacts where no historical data is available (they're a new subscriber, for example), we'll send the campaign immediately.

Time zones and sends to multiple countries

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

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

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