Check your spam folder: It's possible that the email invitation was sent to your spam or junk folder instead of your inbox. Make sure to check these folders and mark the email as "not spam" if it is there.
Confirm the email address: Double-check that the email address you entered for the recipient is correct and free of any typos or errors.
Resend the invitation: Try resending the invitation again. Sometimes emails can get lost or delayed in transit, so it's worth trying again.

I have found a previous discussion regarding gmail. I note that using mxtools.com, my spf recod has not been propagated, nor is the PTR record set. My provider (name.com) says they do not do this because they only provide shared hosting and PTR records are only relevant for VPS and other server solutions. They did not advertise the fact when I bought the domain! So I am tied there for 60 days!

t's possible that the email invite was caught by their spam filter and ended up in their spam or junk folder. Ask your friend to check their spam folder to see if the invite email is there. -Terraria