All emails failed sending with this error message:
‘Message was not executed successfully.
Messenger and Message Type were valid and active, but the messenger send method failed.
The email did not send successfully.
The WordPress wp_mail function is used for sending mails but does not give any useful information when an email fails to send.”
If you go to test an email from one of the email Message template editors, do you receive the test? If so, it may help to go to Event Espresso > Messages > Message Settings and set the the option for emails to be sent on the same request.
If not, can you verify whether *other* emails (like a WordPress password reset email) get sent from your site?
In most cases, setting up a third party service to deliver email will resolve email delivery issues. The built-in mail servers (especially those that are used for shared hosting accounts) can be unreliable. We recommend using a service like Mandrill, Postmark, or any of the other services listed in our documentation for sending transactional email. More info here: