Could be any number of things. Often it’s because you don’t have an SPF record set up.
Contact form 7 is one of the worst form plugins.
Have you checked the server email logs to confirm the issue is the plugin not sending emails, rather than recipients getting the emails flagged as suspicious etc? How’s your spf record looking?
Do you have an SMTP solution? If not, get an SMTP account, for example with Brevo, and then set up SMTP in an SMTP plugin. Without SMTP, email sending from WordPress will always be unreliable.
This likely has to do more with your hosting provider than with the forms plugin. You can place the blame on spammers who have made it necessary to restrict mail functionality.
Some hosts will let you send forms if you set the sender address as one associated with your domain.
Could be any number of things. Often it’s because you don’t have an SPF record set up.
Contact form 7 is one of the worst form plugins.
Have you checked the server email logs to confirm the issue is the plugin not sending emails, rather than recipients getting the emails flagged as suspicious etc? How’s your spf record looking?
Do you have an SMTP solution? If not, get an SMTP account, for example with Brevo, and then set up SMTP in an SMTP plugin. Without SMTP, email sending from WordPress will always be unreliable.
This likely has to do more with your hosting provider than with the forms plugin. You can place the blame on spammers who have made it necessary to restrict mail functionality.
Some hosts will let you send forms if you set the sender address as one associated with your domain.
With others you may need to use https://wordpress.org/plugins/wp-mail-smtp/.
And I agree with those who don’t like Contact Form 7. I use Formidable Forms. Ninja Forms are good too. And a lot of people swear by Gravity Forms.
This issue has become more frequent because of new email rules from Gmail and Yahoo.
You should make sure your DNS has the proper SPF and DKIM stuff set up. And you should also make sure WordPress is sending mail via SMTP.