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You should be cautious of Disposition Actions firing if they send out emails to customers or third parties.
Dates:
Start - for calls that are answered this represents the date/time the call connected (answered). For call that are not answered this represents the date/time that the no. was dialed.
End - when the call ended (was hungup by either party)
Created - the date/time the call record was created.
When - the time the lead was dialed or in cases where the call record exists as the result of a user editing a call, the date/time the record was created.