Where I work we have a fantastic set up to send newsletters, a newsletter editor written entirely in-house that makes it easy to add products (in a variety of styles), signings, competitions, and random text into a newsletter.
We send emails via MailChimp (who are also awesome), so we insert tags into the templates to allow users to unsubscribe, view their profile, etc.
About a month ago I was tasked with adding a bit of new functionality to the newsletters, specifically allowing competitions to be added. So I grabbed a copy of the current template – there was another template as well, but it was named In development (Do Not Use) – and updated it to include the functionality I’d added. Then I renamed the old template indicating it should no longer be used, and that my new template should be.
A month later, it turns out that the unsubscribe link on the newsletter that have gone out since the change were wrong. I checked my new template against the old one, and they were the same, but didn’t match the old newsletters that I had in my inbox.
Then I thought to check the development template, and sure enough, it had the correct code in there. Asked the staff and yes, they were previously using the In development template. I had assumed that they wouldn’t be using the template named Do Not Use.
But, as my old boss used to say, “assumption is the mother of all fuck ups.”
This may or may not be where the phrase originally came from (Under Siege 2):