As far as notifications go, Gravity Forms does not actually send the email notifications. That is 100% handled by your web server. Gravity Forms uses the WordPress wp_mail() function, a built in WordPress function, to ask your web server to send the email notification.
This can happen when you do things such as configure the Send From address of email notifications to an email address that does not use the same domain name as the web site itself. Also, sometimes they can get spammed.
After that, it is entirely up to your web server to reliably send the email. Unfortunately, many web hosts are simply unreliable at handling email properly when sent via PHP. This results in unreliable performance.
The most reliable way to configure WordPress to handle sending email is going to be to use SMTP. You would do this by installing the WP Mail SMTP plugin and then contacting your web host to get the appropriate SMTP settings. You would then need to configure the Send From of your notifications so that it uses an address associated with that SMTP account.
You can also test for theme/plugin conflicts, as we have seen plugins block notifications before:
More reading here:
Posted 7 years ago on Wednesday February 13, 2013 | Permalink