Before investigating why your emails are not sending, try the following items to try and solve the issue:

1. Check your outbox to see if the emails are there
2. Check for internet issues
3. Check if your email account is too full to accept additional emails
4. Check if the email addresses that you are sending the emails to are valid
5. Check if the email service provider is sending out too many emails at once, causing a delay or in some cases an error