When I try to deliver the Burst using "Send Now" button, the Burst doesn't come. There is nothing in spam folder of my Email Client.

When I check Metric Insights Application Errors in Status Monitor I see this error:

MetricInsightsError: Faild insert into email_queue mail_size:2015877 file: /ReportData/iv/engine/libs/Em/Entity/EmailQueue.php line: 87

This Error means that Metric Insights couldn't insert email (with the size - around 2 MB) to the email queue. Email queue is organized by inserting records to the Mysql database.

First thing to do if the above error occurs is check max_allowed_packet parameter size on the Mysql server where database for Metric insights is located and if it's small enough - increase the value to at least 128MB. To know more of how to fine tune Mysql parameters please refer to the following article http://kb.metricinsights.com/m/44498/l/412310-fine-tuning-mysql-parameters.

It is safe to increase the value of this variable because the extra memory is allocated only when needed. For example, Mysql allocates more memory only when you issue a long query or when Mysql must return a large result row.