can I use it with MailOptin plugin and save the author?

but I can’t add the new user as the Author of the new post,

are you trying to create a new user and author a new post at the same time?

Yes, That’s the problem I guess. I use Mailoptin plugin to register the user.

Try to get set your new post to an existing user to make sure you’re doing it correctly, and if that works then likely your new user needs to login before it can become an author….

Are you creating users just to be able to associate a post to them? Or do you need them to log in for other things too?

There are other, simpler, ways to associate a newly created cpt to a form submitter

Yes, I’m only creating them so they can edit the post they posted if the want. If there is a simpler way, I’m all ears ??

So I solved a similar issue during lockdown where a client needed speakers to submit talks for an online conference without actually having a user account.
I created another plugin for CF7 called OTP By Email, which allows you to register and confirm authors with their emails. The OTP plugin creates a unique URL (sent in the notification email) based on the email field. Each time a user clicks the URL they are redirected to a confirmation page. The URL/email mapping is preserved as a transient in the DB and you can identify the current user by their email. An expiry time for teh validity of the URL OTP can be set and expired links will redirect to another page.

Registered users (on the confirmation page) can submit a new post/talk, or edit their existing post/talk. When a new post/talk is submitted and created, add the user’s email to the post as a meta field. It allows you to identify that user’s posts subsequently.

Hope the above is clear.

That looks cool ! Let me try. Thanks !

I’m not sure how to use OTP By Email. Do you create the user with MailOptin or with something else ? Or you don’t use MailOptin, and CF7 and OTP are enough to create the users ? Where should I add the [otp-<field-name>] ? Where is the setting to the notification/confirmation email ? Sorry, I’m a bit confused.

You don’t need to use MailOptin. Create a registration form with CF7 which includes an email field. Insert the OTP mail tag into the notification email sent to the newly registered user along with a message asking them to confirm their email with the link sent to them. On success redirect the OTP link to a new page which as a form mapped with the plugin for creating your posts. In this form you can insert a hidden field (with the CF7 hook) to add the current user’s email. This hidden field needs to be mapped to the email meta field of the created posts.