The admin email is fine however the mail with the download link is not.
yes, this also happened to me. The email by Contact Form is sent to my Yahoo/Gmail email but the download link email was not.
then i figured out that if i used an email address from the same domain, it worked. But the sender is [email protected] (which is not valid email address).
after i had changed the sender address with “email_from” property, i could receive the email in my Yahoo/Gmail email account.
do you use some other smtp plugins or debug plugins? try disable them and try again.