How can I ensure a message is not sent to a user more than once?

If you want a certain message to be sent to users only once without any further repetitions, please add the following conditions to the user segment:

Condition configuration

Condition type

Event count

Event type

mail.send

Operator

equals

Count

0

*The Event Type may vary in case you are referring not to email campaign but any other campaign type.

Event configuration

Event property

campaignID

Operator

equals

Value

Your current campaign ID

Timespan

from beginning of time to dispatch

This condition ensures that the message will be sent only to those users who have received 0 emails (namely, never received an email) from the current campaign since the campaign has been launched.