Use controlled sending with an email campaign

Minimum number of contacts for controlled sending to work

Controlled sending only works if your campaign is being sent to at least 4,000 contacts. Otherwise your campaign will be sent immediately, using the default speed.


If you're an account holder that emails large amounts of contacts in one go, then you may be interested in being able to control and spread the send rate of your campaigns over an even longer period than our default ‘large send’ speed.

This can help protect your email sending reputation with big email providers. Spreading large sends over a period of time will also help ensure your customer service phone lines and resources aren’t swamped should your campaign include a telephone call-to-action.

This article explains how you can control and spread your campaign's send rate.

Enabling and using controlled sending

Our system automatically throttles the send of high volume campaigns anyway, in order to protect your reputation. This is the default ‘large send’ speed and it's still quick, limited only by compliance with send volumes imposed by the ISPs managing the inboxes you're delivering to. 

However, you may wish to control and spread this send rate over a longer period than the default speed allows.

The feature is disabled by default, and can be turned on by following these steps:

  1. Go to Settings > Account > Account settings.
  2. In Features, check the Enable send throttling check box.
  3. Select Save settings.

When choosing your contacts and scheduling your campaign, the feature will appear in the second step.

Select Spread my campaign send over at least: and choose from a range of time periods to spread the send of your campaign over, from 1 hour through to 24 hours.


The send will be broken down into chunks (of 4000 emails) over the time period you've selected.

There are a couple of important points that need to be noted about making use of this type of send, however:

  • Delayed reporting - Reporting won't be available until the whole send has completed. For example, you'll be unable to access any reports for a whole day if you've chosen a spread of 24 hours.
  • Use with paused/unpaused campaigns - If you're using controlled sending and have paused and then unpaused a campaign, be aware that the assured time of the spread send will no longer apply. This is because the remainder of the unsent emails will be sent immediately upon unpausing.

Alternatively, you can select Optimised to send your campaign using send-time optimisation. This will start sending your campaign immediately but will optimise the time of individual sends to maximise open rates based on your contacts' historical opening behaviour. The campaign will optimise over a period of 24 hours from the initial time of sending and will remain in the outbox until complete.

Send time optimisation isn't available for a split test or scheduled campaigns.

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