My colleague had problem that she could not receive mail from customer, I already followed these step.

Check in spam mail -> nothing there.

Check on receiver name -> correct.

As customer if they receive any returned mail -> none.

All I can say that, mail was already sent from customer. Reached to zoho server but look like the mail could not delivered.

Please check.

PS: I attached the mail form customer to my colleague, please check on it.

Thanks.