Emails not received by a customer

New Member
1 0 0


I have a customer who has told me they did not receive any emails confirming their orders or that it has been shipped. This customer has bought from my store before and has received confirmation emails before however on this occasion she did not receive any.

She has a gmail account and confirmed the email she entered is the correct one.

I keep getting the emails sent back to me on the Undelivered Mail Returned to Sender.

Please help