Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain gmail.com by gmail-smtp-in.l.google.com. [2a00:1450:400c:c0a::1b].
The error that the other server returned was:
550-5.1.1 The email account that you tried to reach does not exist. Please try
550-5.1.1 double-checking the recipient's email address for typos or
550-5.1.1 unnecessary spaces. Learn more at
550 5.1.1 https://support.google.com/mail/answer/6596 b6si14428911wiy.124 - gsmtp