Set up a WP site. 3.5.2 Contact Form 7 installed. Visitor completes form, contents of the form go to the site owner as an email, and a thank you response email goes to the site visitor. All fine and good.
Update WP to 3.6 re-test.
Visitor completes form, contents of the form go to the site owner as an email. Thank you response does NOT now go to the visitor. No error codes, no bounces.
Nothing has changed but 3.5.2 to 3.6.
Any suggestions?