You could always try checking for a theme/plugin conflict by following the instructions here:
I have seen instances where a plugin that was trying to utilize the WP_Mail incorrectly was interfering.
@akelsall - This isn't an issue with Gravity Forms - notification and email sending is going to be up to your host to send out. There are a variety of factors that come into play with email reliability and none of them are things Gravity Forms itself controls. Gravity Forms simply passes the Send To, Send From, Subject and Message of the email to the core WordPress wp_mail() function and that is where it's involvement ends. It is then entirely up to your web server to reliably send the email.
The best article I have found that discusses how to make your WordPress site more reliable at sending email is this one by Joost de Valk:
His article discusses improving email reliability for comment related emails sent by WordPress. But it is directly applicable to email reliability with Gravity Forms because both of them use the same core WordPress function to send email the exact same way using the wp_mail() function.
Posted 10 years ago on Tuesday June 19, 2012 | Permalink