Verify email address and all other pertinent contact information has been entered correctly.
Follow-up with your contacts after sending the initial email to verify they have received your email.
Remove the auto email event from your contact if you want them to stop receiving auto emails for a period of time. Do not remove your contacts email address if you have an active auto emailing event set up for them.
Check your Contact Summary Report (click on Contacts from the main menu, then Contact summary) to see if you have any contacts that have opted out of receiving your emails. Use this as an opportunity to get in touch with your contact and find out why they have opted out. Then remove contacts if desired.
Check My sent e-mails regularly (click on Contacts from the main menu, then My sent e-mails) to see the Hit Count for the emails that you have sent. If they have viewed a link multiple times, they may be interested in a property that was included in the link that you sent them. To view the content of the email click on View in the Content column in the respective row.
Remember that one contact may have multiple e-mail addresses and multiple searches.
Either delete inactive contacts or create a group for them and remove the auto email event.