Hello,
I’ve been trying for a few months to find a solution to this problem that seems to be chronic and I’ve found complaints of the problem that are over a year old.
I manage several sites with contact form 7 and they are all having the same problem of sending with duplicity with a difference of seconds between one and the other.
Today I created a new wordpress installation and installed and configured contact form 7 for a new website and it had the same problem.
It seems evident that it is a problem with the Contact Form 7 plugin, regardless of what is installed along with it.
I hope there is a solution to the problem, because although it is an excellent plugin, we will have to look for other solutions if there is no solution.
Here are some of the many related and unresolved topics.:
https://www.ads-software.com/support/topic/duplicate-entries-and-emails-after-submitting-contact-form-7/
https://www.ads-software.com/support/topic/contact-form-7-sending-multiple-emails/
https://www.ads-software.com/support/topic/duplicate-emails-sent-3/
