Contact Form 7 – not sending email when email field has yahoo/hotmail address

I have a simple form — just 2 fields, Name and Email address. When I enter a yahoo or hotmail email address in the form, no email is sent even though the message for successful sending appears after I hit Send. Email is sent successfully when the email address entered in the form is gmail or any private domain email address.

I’m using WP-Mail-SMTP plugin also… The “To:” in the Mail section of the Contact form setup is to a private email and the same email is in the From of the WP-Mail-SMTP setup….not sure it matters….