Not getting family invite email

[Flowlance]

As title says, my family member is not receiving the invite email. Email server at hotmail.com. Her email has some capital letters in it, but spotify only accept typing in all lowercase letters. Not sure if it's case sensitive or not.

I tried debugging the html5 input field and adding "novalidate" to the email field, and it allowed me to send the invite (this might be against the rules, as it's exploiting your validation lol. Sorry if so) . But it's still not being received in her inbox. 

Can you see in your outgoing mail logs why it's not being delivered?

thanks