I was having the same issue: No emails were sent via FormIt, and I received the ominous "You must provide an email address to send to" error message, although I had specified the address with &emailTo (and I did not forget to add the "MyEmailChunk").
Finally I got it to work

(just by accident) after changing
mail_use_smtp from "Yes" to "No" in the system settings

.
But: I am on GoDaddy shared, which for sending e-mail requires to specify smtpout.secureserver.net as smtp server, my email address/username and password, as far as I understand.
So, if MODx ist not using SMTP, how is it sending mail at all? I am not using the SMTP snippet call from the docs example either, just
Sorry for asking such noob questions, but I really would like to understand this MODx e-mail magic. Would anybody bother to share their knowledge?
Thank you and my best greetings,
Alex