In order to comply with the SiteGround e-mail Terms of Service you have to configure your AcyMailing Joomla extension to send less than 400 messages per hour.
The task can be completed from the Joomla admin area->Components->AcyMailing->Configuration->Queue process.
In the Manual send process configuration enter the following values:
Send 40 e-mails and then wait 6 Minutes before sending an other batch.
More details about the AcyMailing configuration can be found at:
http://www.acyba.com/en/support/documentation/55-acymailing-config.html
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