Deliverability: where’s my email?

It’s that time of year again - Singles Day, Black Friday, Cyber Monday, and can I say the dreaded C-word yet? Okay, okay, I’ll wait until after Thanksgiving to mention Christmas. Oh, oops, sorry!

Anyway, it’s time to answer my second favorite seasonal question (my first favorite is “would you like more roast potatoes?” and the answer is obviously yes) – where is my email?

Email is awesome – it’s cheap, versatile, and generates a tonne of ROI. It’s also pretty fast in most cases, but it’s not instantaneous. There are a bunch of reasons why there might be a delay between you hitting send and the recipient seeing the email in their inbox. Let’s explore some of the causes and then talk about how we can avoid them.

Email is not an instant medium

The journey of an email doesn’t end after it’s travelled from mailserver to mailserver between your email service provider (ESP) and the mailbox provider (MBP). It then goes on an adventure through layers of filtering checks – sometimes involving relay through third party filters – and the MBP’s infrastructure before it’ll appear in the inbox.

During busy periods, the filters and infrastructure are handling a lot; last year dotdigital alone sent over double our usual daily volumes on Black Friday.  The huge jump in the number of inbound emails can mean that the journey of a mail through filtering and infrastructure to the inbox is slower than usual. MBPs like Gmail, Hotmail, and Yahoo are likely to prioritize 1-to-1 emails if they’re busy, so you might receive Great Aunt Erma’s festive update email (she should really add an unsubscribe link) before marketing mail appears.

Mailbox providers are under high load too

This time of year is when I, a humble mailserver engineer, am most likely to see problems with connecting to overloaded MBP mailservers. You’re not the only brand sending emails – pretty much everyone else is as well. And while MBPs have ways to scale up their operations during busy periods, occasionally they can’t quite keep up.

Sometimes they’ll be unable to handle even one more inbound connection, and sometimes they’ll be metaphorically yelling via SMTP error messages to slow the heck down. Depending on how distressed the recipient mailserver is, it may be wise for your ESP to automatically slow down sending a bit so as not to further overwhelm it. This means it’s less likely that it’ll get really frustrated with senders and slow them down even more – or worst case block them. The mail queues do get delayed a bit, but once the recipient server recovers then it’s full steam ahead.

Sending reputation matters

The better your reputation as a sender, the faster your mail will be accepted by MBPs. 

Particularly for larger sends, if you have a poor reputation or the MBP deems your email in some way suspicious, they may release some emails to the inbox and then wait and see what recipients do with those emails. Depending on how their users interact with this first batch, the MBP will decide whether to deliver the rest of your emails – and to where (inbox or junk). 

If your reputation is really rather poor, the receiving mailserver might temporarily decline the inbound connection and tell the sending ESP mailservers to try again later. This means the mailservers will wait a period of time (customized for the specific MBP the email is going to for optimum results) before attempting delivery again

Preventing delays

There are a few things you can do this holiday season to avoid delays to your emails. 

  • Follow deliverability best practices when it comes to data collection/hygiene/management, and send highly engaging content to people who really want to receive it. Our 6 Cs of deliverability are a great place to start.
  • MBPs don’t like sudden changes in your sending patterns. If you’re planning on sending more email that you would usually do (and let’s face it, who isn’t?) make sure you gradually ramp up to that volume over a couple of weeks before your biggest sending day.
  • Send to your most engaged recipients first. This primes the MBP with lots of positive engagement indicators, and makes it more likely they’ll accept the rest of your mail quickly and hopefully put it in the inbox. For dotdigital customers, Engagement Cloud does this for you automatically. Sweet!
  • Don’t schedule your sends for the top of the hour, and avoid 15min, 30min, and 45min after the hour as well. Most senders schedule campaigns for these times, and MBPs see enormous spikes in traffic that make delays more likely. Try multiples of seven instead – e.g. try 9:07am instead of 9.00am, or 5.49pm instead of 5.45pm.
  • We’re here to help – always, but especially during this business critical season. If you’re using dotdigital and have any questions about deliverability or email delays, then please do get in touch and our awesome experts will provide advice to help you get back on track.

Of course, no one can help it if a MBP has difficulties or an outage over the festive period, but by following the above guidance and planning your holiday sends carefully, you can minimize the risk of delayed emails.

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