No not your auto-responders in your email campaign service. Those pesky things people in fancy offices turn on when they go on vacation.
Schedule an email to go to a decent sized segment of your email list. I would say minimum of 100 people to get a good sample size.
Now this is going to go against everything in your soul, trust me it hurt for me to do it too. Schedule the email to be delivered on a national holiday like Christmas, or New Years day.
Don’t send a holiday email(those are the worst), treat it like it’s part of a normal campaign. Just in case someone actually opens it.
Where is the hack? The hack is testing your deliverability and if your emails are going to spam.
If they are going to spam the auto-responder is likely to still respond. And TELL you it’s in spam!
Most exchange based email servers will still reply to even things in the spam folder. Automatic reply: [SPAM] is what I usually see come back.