Email deliverability: everything you need to know

Posted on: April 24, 2020

Reading Time: 5 minutes

Category: Prospecting


Email deliverability: Everything you need to know

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The legacy of spam – and its ongoing challenge – has meant that email deliverability is a major concern for any business sending emails.

Or, at least, it should be.

As many as 17% of emails sent never reach their intended inboxes. That’s just about one-fifth of your revenue earning potential shot in the foot.

Your sender reputation is a critical factor that affects your email deliverability. Quite simply, senders with a good reputation get their mails delivered but senders with poor reps will get either blocked at the gateway or see their messages land in the barren space that is the junk folder.

Right now, let’s give you the low-down on low email delivery rates.

And then you have no more excuses.

Recipient engagement

Recipient engagement and is based on sophisticated analyses of how your recipients handle the mails they receive from you.

Reading, forwarding, opening, clicking on or storing your mails are all positive signals, as is adding your address to their contacts.

Negative factors include ignoring, deleting without reading, unsubscribing or marking as spam.

The content of your emails

Content doesn’t just mean the words you use – although there are plenty of these that will trigger spam filters.

Avoiding spam filters also means considering things like:

  • The images you use
  • The templates your mail is based on
  • The links within the mail
    (such as avoiding using URL shorteners, such as
  • And subject lines
    (such as avoiding using question marks)

Spam complaints

These are messages marked as spam by the recipient.

You only need to hit spam complaint rates of 0.2% to start the alarm bells ringing. And, if you think that’s low, watch out for Gmail, where an infinitesimal spam complaint rate of 0.08% will have you flagged as a potential spammer.

Spam traps

Spam traps fall into two categories.

Recycled spam traps are email addresses that should not be receiving mail because they haven’t been used in such a long time. Pristine spam traps are addresses that have never even signed up to receive mail.

Sending mail to any type of spam trap is like a wasp falling into a honeypot (and this is how AOL refers to them). It reveals that you aren’t maintaining a clean list or are purchasing bad data.

The best and only way to avoid pristine spam traps is to never purchase email lists or scrape the web for emails. And for recycled spam traps you need to remove recipients regularly who don’t respond to your mails.

Email addresses

The email address your mail is sent from is considered in the spam mix, as are the email addresses you send to.

Sending email to a large number of invalid or non-existent email addresses sends a negative signal to inbox providers. Always check for typos in email addresses entered and remove addresses that bounce from your lists.

Another way to avoid issues rising here is to use double opt-in when adding prospects to your list.

IP and domain reputation

This is based on how ‘spammy’ your domain and IP address currently are or historically have been.

If you’re sending large volumes of mail (say, over 50,000 per month) having at least one dedicated IP address is the safest way to protect your reputation from other senders who share the address.

You may also wish to consider segmenting email activity – typically by transactional and marketing activity or between different brands. This helps protect reputation bleed – where the poor reputation of one area starts to affect the deliverability of another.

For cost reasons having a dedicated IP address or segmenting emails may not be practical for smaller senders, but do choose your IP address provider carefully.

Something that is essential for all senders, however, is authentication and verification.

  • Make sure you have an SPF (Sender Policy Framework) to identify which IP addresses are allowed to send email using your domain
  • Further consolidation of your reputation is available from A records that point your domain to an IP address and rDNS that links your IP to your domain
  • In addition, installing DKIM (Domain Keys Identified Mail) ensures that the message that reaches each inbox provider has not been changed in any way from when it was sent from your servers. Because this defends against ‘hacks’ it does you a lot of favours in the reputation stakes.
  • If your sending domain can’t receive mail, or it lacks a valid mail exchanger (MX) record, some inbox providers will block your mail. It is also best practice to allow the ‘from’ address to receive mail directly.


As well as monitoring each mail themselves, inbox providers also use external sources of information. These are known as blacklists.

It’s important to realise that just appearing on a blacklist doesn’t spell doom and gloom for your ROI from email activity. Some blacklists carry much more weight than others. You can check to see if you’re blacklisted – and where – using this handy, free tool provided by MXToolBox.

Good to go?

So, there you have it: email deliverability served on a plate.

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