Is it possible to have emails resent to customers?
There are a few options for resending emails to customers. One of the scenarios in which you might want to do this is, for example, if the emails were sent to Mandrill but Mandrill rejected them and didn't actually deliver them.
MageMail has a record of every email sent and it won't resend an email for a given trigger to a customer that already received the email for that trigger.
One way around this is that you could clone the email trigger and archive the old one. For example, let's say you have a Winback sending to customers from 90 to 120 days out from last purchase. All of those emails somehow didn't get sent out or need to be resent.
You can clone that email and archive the original one. The new trigger will send to those customers again since it's a new trigger and doesn't have a record of already having been sent to them.
Just be careful when going this route to avoid sending a lot of duplicate emails to customers.
Also, keep in mind the sending window's that are involved. If the Winback 90 to 120 days ago was sent out 10 days ago, and you want to resend to that same group of people, your new trigger would need to be targeted to customers 100 to 130 days out.