"Invalid email address" error for non-compulsory email field

Hi, One person who has tried to submit one of my forms from a mobile device keeps getting the error message "Enter a valid email address". She has attempted three different valid email addresses, and I have attempted making the field non-mandatory, but the same message still appears. 

Other users have managed to submit the form successfully, perhaps from a PC instead of a mobile device.

Could you please advise? Screen shot below.

Thanks in advance!

Ok, so I worked out the answer to my own question. :-P

The issue was that I was using an "email" field for entry of a phone number. Well, der.

Hello @laracam, We are glad that you were able to resolve this issue. Feel free to get in touch should you have further concerns.