Wanadoo mails do not arrive anymore

My client has an email address myclient@wanadoo.fr

For about 8 days, he no longer receives emails from forms his website.
This site is created in WordPress and the forms are generated by the Contact form7 plugin.
The configuration of the site has not changed for 5 years, the whole site is kept up to date (theme, plugins, WordPress)

4 forms are available on the website and the settings of the forms all send to myclient@wanadoo.fr.

Since about 8 days my client no longer receives emails from forms on his website.
They do not appear in his webmail.

My client has an email address myclient@wanadoo.fr

For about 8 days, he no longer receives emails from forms his website.
This site is created in WordPress and the forms are generated by the Contact form7 plugin.
The configuration of the site has not changed for 5 years, the whole site is kept up to date (theme, plugins, WordPress)

4 forms are available on the website and the settings of the forms all send to myclient@wanadoo.fr.

Since about 8 days my client no longer receives emails from forms on his website.
They do not appear in his webmail.

A simple email sent directly to this same address (myclient@wanadoo.fr) arrives in the inbox (webmail) without problem

Test on my client’s website:
Host: WP Engine
Domain: OVH
Plugin contact form 7
Type: WordPress

Form7 contact plugin

Form test with mail on myclient@wanadoo.fr
No mail received

Modification of the mail of reception of the forms of the Internet site:

myclient@wanadoo.fr> webmaster@aglae.fr
myclient@wanadoo.fr> webmaster458@gmail.com

Form test with mail on webmaster@aglae.fr and webmaster458@gmail.com

2 sets of test forms have been sent on 2 different e-mails (webmaster@aglae.fr and webmaster458@gmail.com)> test ok mails received

Test sending forms from the website completely different from another client to me: https://another-client.com/test-mail-2/
Domain OVH
OVH Hosting
Plugin contact form 7
Type: WordPress

Creation of a test form on this site with 2 email addresses recipients: myclient@wanadoo.fr and webmaster@aglae.fr
Reception of the email at my home (webmaster@aglae.fr)
No reception on myclient@wanadoo.fr (outlook 365 webmail and Orange pro online portal)

Installing the “CaptainForm” form plugin on my client’s website, creating a test form with myclient@wanadoo.fr and webmaster@aglae.fr

Mail received on the mailboxes myclient@wanadoo.fr and webmaster@aglae.fr.

Do you know any problems with wanadoo.fr mail addresses (blacklistage or other?)

Do you have a track to fix this type of failure

thank you for your comeback
Of course, Access to the admin privately