Using send time optimisation


Sending a time-optmised campaign
Compatibility with other features
» Compatible
» Not compatible
How it works
Also note...


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


This will start sending your campaign immediately, but will optimise the time of individual sends to maximise open rates based on your contacts' historical behaviour.

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 optimise over a period of 24 hours from when you send, and remain in the outbox until complete.

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

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

Scheduled campaigns

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

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 (via 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 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 open behaviour in the sending account will be used.
  • The 24 hour optimise 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 optimisation is deliberately time zone-agnostic. When an optimised 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-optimised campaigns are strongly recommended.


AudiencePoint are specialists in email send time optimisation, and a partner of ours. Although smart, our implementation of send time optimisation has limitations in terms of its functionality in comparison to theirs. For example, AudiencePoint uses all of their data in their predictions, and not just the data that belongs to the client. AudiencePoint also allows the optimisation period to be user-defined. If you really wish to advance in this area, we certainly recommend using them.

Have more questions? Submit a request


  • Avatar


    Do you have any statistics surrounding how much using send time optimisation could improve your open/click through rate? Or is it too much of a new function to say?



  • Avatar

    Hi Helen,

    Yes, this is still a very new function, so we don't really have any official statistics.

    However, we have had reports of 6% increases in open rates, and that comes with a high degree of confidence attached to that.

    That said, of course, your own circumstances may make the biggest difference.

    We'd recommend that the best way to find out the difference that send time optimisation could make is to give it a go. For instance, pick one of your typical mailings (a newsletter, for example) and send it using send time optimisation over a number of months, comparing the results using our 'compare campaigns' tool in reporting.

    Alternatively, you could create a random sample of contacts and then send them the same campaigns as the rest of your contacts but with send time optimisation turned on, so they then become your 'test' group. This will provide you with more accurate results. If all goes well, your test group will show the better results and you will be able to really gauge what the function is doing for you.

    Whatever you choose to do, I hope something from the above has helped you out!

  • Avatar

    Is there a report that you can run that allows you to view the open times by recipient of all historical campaigns? Even something like a simple bar chart with times along the x axis and number of opens along the Y axis. If there is already I can't find it and would like to have that control myself for following campaigns to send

  • Avatar

    Hi Julian,

    Thanks for your question. We don't offer this type of report.

    This is because our internal method for working out optimised sending times doesn't just look at historical open times but does a lot more analysis with it.

    Have you been able to try the feature out, by the way?

  • Avatar


    just a comment:

    Looking at reporting before the 24 hours is very confusing. I've just looked at an optimised campaign report and it seems to show the full list as "sent" and "delivered" (apart from bounces) even though it is still in the outbox so presumably not all have been sent yet.

    I'll wait the 24 hours next time!

  • Avatar
    Hi Neal, I realise you can't use this with a scheduled campaign but wonder why not?. We like to send at the weekend using optimised. I don't see why we can say 'start to send at 2pm Saturday'? It would be helpful as otherwise someone has to log in at the weekend to send the optimised campaign. Is there a logical reason why this wont be developed? Thanks, Mike
  • Avatar

    Hi Mike,

    Thanks for raising this. Our current sending logic is underpinned by the fact that a campaign is either sent immediately, scheduled or optimised. Thus you can either decide when a campaign is sent (immediately or scheduled), or we decide when it should be sent (optimised). There is no in between as it stands.

    We appreciate where you're coming from though. If we felt there was enough demand for it, we would then look at scheduling further development. There is already a feature request along these lines here, which I’d recommend voting for -