How is COVID-19 affecting global email traffic?

MailChannels delivers email for hundreds of web hosting providers. When your web site needs to send out a password reset, or if you send a message from your hosting webmail, there’s a decent chance that it passes through our infrastructure. We also filter out spam and phishing messages that originate from hacked web sites and email accounts. As such, we have a pretty universal view of the email coming from web servers and small businesses who host their mailboxes with these services.

I was curious as to whether the COVID-19 pandemic has caused any changes in the nature or volume of email we process, so I consulted our petabyte-scale logging tool to pull out some valuable insights. The results are interesting.

First, when we look at the average volume generated each day by a customer, it’s actually higher than any of the preceding three months – in fact, the average daily volume in March is the fourth highest in the past two years. We know that people are working from home these days and also that many COVID-19 related messages are being sent to update customers, employees, partners, and other communities about this unprecedented situation. Clearly all that electronic communication is having an effect on email traffic.

Next, let’s take a look at messages that seem to relate specifically to COVID-19. If I search our logs for the term “COVID” in the subject line, an obvious growth trend jumps out as shown in the following chart:

The term “COVID” started appearing in earnest around March 11th, increasing by over 1,000-fold vs the volume seen in late February. Interestingly, we blocked far more “COVID”-related messages than we delivered. Widespread reports of scammers using COVID-19 as a pretense for phishing attacks is most likely the reason for this high ratio of blocked messages. Phishing aside, “COVID” is still close to 250 times more prevalent than it was a month ago.

The effectiveness of our efforts to block COVID phishing attacks is evident in the delivery statistics for our outgoing email. The following chart compares the fraction of messages with “COVID” in the subject line that we accepted from customers’ servers vs. the fraction of those messages that we were able to successfully deliver to receivers on the internet:

By aggressively rejecting incoming COVID-related phishing attacks, we have been able to ensure that an average of 95% of COVID-related messages are being received by email receivers. We assume that the majority of these received messages are, in fact, legitimate communications about the pandemic. I note that our acceptance ratio hit less than 70% on March 18th when we saw a particularly large wave of COVID-related phishing come through our service.

We will keep you up to date as COVID-19 continues to generate waves in the email world.