In the past miners would take a caged canary into coal mines. It wasn't to help them whistle while they worked though.
If the miners hit a gas pocket, the canary would die before the gas got strong enough to kill the miners.
The canary was an early warning system for the miners. Which is where the phrase "canary in a coal mine" comes from.
For years now, I've had my own canary in a coal mine when it comes to email marketing. And it's paid off on multiple occasions.
I sign-up for my own email marketing list multiple times.
I have my business account.
I have my Gmail account.
I had Hotmail, Yahoo, and other free accounts in the past too.
Whenever an email would be sent, I would expect to get copies of the email.
If my Gmail one was missing, then there's something going on with Gmail. Maybe there was a delay. Maybe it got classified as spam. Maybe Gmail blacklisted my email server.
Or if all of the emails show up hours after it was supposed to (or hours early) I'd know something got screwed up with the scheduling as a whole.
I might not know exactly what the problem was, but I would know something odd was happening and I'd have a canary chirping at me to look into it. Often I'd find the problem before anyone else, sometimes even the email providers.
These act as early warning systems for my email marketing that I could react to.
All this for the cost of a few extra subscribers and some emails that you'd archive now and then.
(All of these scenarios have been actual ones I've experienced with various email providers)
If you do email marketing, this is a simple canary you can setup. You don't need any fancy automation or to pay for a deliverability system. Just signup for multiple email accounts and have them forwarded to your main email.
If you haven't installed Repeat Customer Insights yet, it's an easy way to get a detailed look at your customer behavior.
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The cohort analysis in Repeat Customer Insights will automatically build cohorts for all of your customers. It has the ability to go back through your entire store history so you can get a complete view of your customer behavior.