The trick is to wait for the right email to reply to. Some criteria to look out for:

1. Watch for a email sent to you and one (or more) of your company’s important clients by a co-worker (that won’t slit your car tires after the prank)
2. The client’s email addresses must be easily altered in a way that your co-worker won’t notice they have been changed
3. Think of something funny to reply. Call your co-worker a douchebag, reveal something embarrassing about your co-worker, make a sexual remark  to your co-worker or about the client (be careful with this), make a rude comment about the client, etc.

Once you have a good email picked out to reply to, write your message to your co-worker. Once it’s good to go, add in the clients email addresses but change them creatively while replicating the scenario of an accidental ‘Reply to All’.  For instance, ‘bobvance@rrmachinegroup.com’ could be changed to ‘bobvance@rmachinegroup.com’ or ’sarahjacobsen@thewebgroup.com’ could be altered to ’sarajacbosen@thewebgroup.com’. Something you think that your co-worker wouldn’t catch at first glance. Make sure you change the name enough that it won’t go to someone else in the company/domain! Also, it is good practice to triple check your work here… because a mistake could be devastating for everyone.

After sending the email, expect a frantic call or text message  from your co-worker in about 15-30 minutes! Start by playing dumb and decide how far you want to take it. Good luck!

I have provided an example below:

To: seth.johnson@mycompany.com; valeriesmith@thelaborgroup.net
CC: someoneelseinontheprank@mycompany.com
Subject: RE: Follow-up on content for the brochure cover

Seth,

Don’t hold your breath on that content, Valerie is a pain and has been dragging on this. I know you have a big crush on her though, so I guess we can manage to deal with it for now…

-Your Name

—– Original Message —–

From: seth.johnson@mycompany.com
To: valeriesmith@thelaborgroup.com, me@mycompany.com
CC: someoneelseinontheprank@mycompany.com
Subject: Follow-up on content for the brochure cover

Hi Valerie,

I am just emailing you to see if there is any progress on the brochure cover content.

Thanks,

Seth