Bvckup blog. Assorted notes on the design of fast real-time backup software.

Just a quick post to share something that seems obvious in retrospect, but took a while to notice and fix.

A mailing list for those wanting to follow Bvckup and Bvckup 2 progress has been up and active over a year now. Subscribing to the list triggers a typical confirmation email with a link that needs to be clicked on. The odd thing was that a good half of those subscribed never bothered to do that.

So last month, after receiving a small rush of sign-ups from I decided to put things in order and run a bit of A/B testing. Good thing I did.

Simply changing the email subject from this

to this

increased the number of completed subscriptions from 51% to 82%.

The original subject read like… well… a confirmation rather than something that requested an action and people simply did not bother even opening an email. A simple but costly oversight that took me almost two years to realize.


There is a thread for that: