Seeing emails like the following in your Inbox, especially after being away from the office?
This is an automatically generated Delivery Status Notification
THIS IS A WARNING MESSAGE ONLY.
YOU DO NOT NEED TO RESEND YOUR MESSAGE.
Delivery to the following recipient has been delayed:
Message will be retried for 2 more day(s)
Technical details of temporary failure:
The recipient server did not accept our requests to connect. Learn more at https://support.google.com/mail/answer/7720
[(0) firstname.lastname@example.org. [18.104.22.168]:25: socket error]
This is an excellent case of “computers are stupid”.
Chances are a newsletter was sent to you from email@example.com while you were away from the office.
The auto-responder you set to kindly inform people of your absence didn’t know that it was an automated newsletter message, so it did its job and auto-responded.
Unfortunately, the sending address, firstname.lastname@example.org, likely doesn’t exist, or is set up to reject emails to it.
Your mail server of course doesn’t know that, and is stubborn, so the “Message will be retried for 2 more day(s)”.
Just ignore it. You’ll likely get several more of these over the next few days as computers senselessly assault each other with unnecessary and unwanted responses.