[slartibardfast0]

I have a first.last@gmail address from the beta, and after numerous misunderstandings I've learned to use very precise language when attempting to help:

First establish that they're speaking to the wrong person.

Then suggest the nature of their mistake is a simple omission of a letter or number.

never offer a 'no big deal' or de-escalation until they've acknowledged the problem, otherwise the real recipient will never get the email!

[cwkoss]

Reply with this - people are less likely to argue if they think you are a robot:

This message was created automatically by mail delivery software. A message that you sent has not yet been delivered to one or more of its recipients after more than 24 hours on the queue on mail.example.com.

The message identifier is: 1JYIJ1-0008Ew-JK

The date of the message is: <date>

The address to which the message has not yet been delivered is: <your email>.

[slartibardfast0]

oh I did try that approach! it was generally ignored completely except for one hilariously angry person.