It would be incredibly useful for the email communications to be intuitive. Scenarios include:
Having the option to schedule a resend of an email if it hasn't been opened in a set time period (say 3 days).
The ability to create sequences and triggers. For instance, Year-End appeal is emailed to a set recipient list and as recipients make an online donation from a link in the email, they are removed from any follow up emails from that sequence. It triggers them to be moved to a different sequence. Likewise, if a recipient doesn't interact with the initial email, they can automatically get a follow up email.