This just started happening and have found a reference to the error. Recommendation is to contact the developers so here I am.

Here's a link discussing changes to Joomla that effects sending mail:

http://joomla.stackexchange.com/questions/16051/fix-the-invalid-address-error-after-upgrading-to-joomla-3-5-1

I have latest greatest version of RSForm Pro. Joomla is up to date, and we are using PHP 7.
The site is working fine. The registration form is also working and sends out both user and admin emails as expected.

The problem is when filling out the registration form (RSFP registration form linked to joomla registration), it submits fine, indicating the registration was submitted correctly, but there is a big joomla error box (joomla error from template) saying "invalid Address", and in the error it shows the email address and Full Name separated by a comma.

Everything else works. The email confirmation to the user works and activates accounts just like before, but we can't have a big error popping up when it isn't true.

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hallo, solution?

in my site have this problem:

formazzaevent.com/index.php/join-us

after send module, a message "invalid Address"......