Here are some suggestions that could help resolve the issue:

1. Check corrected spelling, case, and punctuation
   Make sure that the email address is spelled correctly, using the case (upper and lower) as intended with correct punctuation in order to get the message.


2. Check the recipient’s vacation responder
   The vacation responder can be set to reply to a sender with a cutesy message, for example, instead of receiving the actual user’s email.


3. Check the recipient’s anti-spam filters or junk folder
   If the message was considered spam, it may end up in the recipient’s anti-spam or junk folder.


4. Try sending the email again
   Sometimes, emails are delayed and need to be resent.