Your business circumstances have changed. The email marketing world post lockdown will ensure that, not only for you but for the subscribers to your email marketing lists as well. Carrying on as before is not an option. Your working practices will have to change to cope with the enforced new reality.
Key Performance Indicators (KPIs) and metrics depend a great deal on comparisons with those gone before. In a world where many companies will be chasing subscribers to email marketing lists, the 
cost per lead is likely to increase. By how much is anybody’s guess at the moment. You might feel that now is the time to make educated assumptions, so for a while all the metrics will show is whether or not your guesses were correct. For an indeterminate period, obtaining the returns will be all you can usefully do.
Some will probably remain at the old levels. Traffic to lead ratio is probably one of those, as if someone visits your website, or clicks through to your landing page from a newsletter, the percentage you turn into conversions is likely to remain more or less the same. On the other hand, return on investment will probably take a hit in the short term.
Returns from your email marketing software might well give indications as to the likely changes that you can look forward to. For instance, certain products might well be less popular than before. On the other hand, those items which still sell strongly, perhaps even increase, will give you a clear signpost as to where you can expect profits to come from initially. Do you concentrate on the positives or go after rebuilding the sales of those products not selling so well? It’s a difficult choice, and one that might be critical.
To put it simply, for many KPIs and metrics it might well be a case of starting over. It’s possible that you will look back at your pre-lockdown unsubscribe rate as the good old days given the probable high unemployment levels.
I don’t particularly like the term ‘new normal’, but it’s a pretty good basis on how to treat your old KPIs and metrics.
