Trigger emails are emails that are sent according to cutomers action or a piece of data that tells us something useful about the recipient. Again timing is very important. Some examples are..
-Welcome messages (a response to a sign up)
-Emails sent out on a customer’s birthday (targeted promotion will also increase open rates)
-Post-purchase follow up emails (like other recommeded products/ services for you..Amazon are good at this)
-Email sent to a customer who viewed an item online, but did not complete the transaction (like customer’s leaving at checkouts..remarketing can make a difference and increase conversions. Give them an additional incentive like free delivery to complete the transaction.)
-Pre orders (stock updates)