Guide To Email Deliverability

What is email deliverability

Email deliverability is the measure of how successfully you’re able to get your emails delivered to your recipient’s inboxes. It’s a simple concept, however terminology such as feedback loops, blacklists, DKIM can become a little confusing and even daunting.

However the reality is that if you follow simple best practice advice you shouldn’t have any problems.

Why does deliverability matter?

Your deliverability is arguably the most valuable asset your email marketing has. Without looking after it you may find that your emails aren’t being delivered to your recipients. To avoid all of your email marketing efforts going to waste, it’s important to get deliverability right.

What affects deliverability?

As you’ll discover there is no exact science to getting your emails delivered to your recipients inboxes, and there’s certainly no magic trick to getting it right. The reasoning for this is that ISPs such as Gmail and Yahoo are constantly evolving and developing new ways to protect their recipients from unsolicited spam. There are lots of different factors that ISPs look at, and to varying degrees it depends on the particular ISP.

Your data and how you collect it
The most important way for ISPs to determine whether to put your email into someone’s inbox, their junk folder, or simply not deliver it at all, is to look at how people have responded to emails from that sender before. Therefore the best way to ensure an inbox placement is to make sure that all of your recipients want to receive your emails.

Ensure that when people sign up, you’re as transparent as possible and are setting expectations of contact. For example, tell people what you’re going to send them and how often, so that they aren’t surprised when they receive your emails.

Offer recipients preference options when they sign up, for example they might not want to receive all of your emails, so have a preference centre in place that allows recipients to specify exactly what they want to receive from you.

You could also use a double opt-in email which asks recipients to verify their email address when they sign up. This ensures that the email addresses in your list are as legitimate as possible.

Lastly, make sure your privacy policy is publicised. Not only is this a legal requirement, but this will help people feel secure when they sign up.

Your sender reputation
Once people are signing up to your email list, keeping them engaged is absolutely key. Have a look at the strategy section further down this down for more details.

Apart from your engagement levels, other important factors to consider that affect your reputation include:

Complaints – Even a tiny number of recipients marking your sends as junk can severely impact on your overall deliverability.
Bounces – ISPs will also look very carefully at your soft and hard bounce rates. If you send to addresses which are no longer valid this will generate a bounce. These are seen as a sign of poor list hygiene and could result in your sends getting junked.
Spam Traps – These are usually old email addresses that are left active as ‘traps’ for marketers with bad data sourcing methods. Once emails are received, the sender is identified as one with bad data collection methods and is usually blocked by some or all of the major ISPs.
Sending Volumes and Consistency – ISPs prefer that you have a consistent pattern of sending. If you suddenly increase your sending overnight by a large percentage, or have a large spike in volumes after not sending for a week or two, it will probably result in inboxes being very wary of your sends and any higher rates of emails being deferred.
Blacklists – These are lists of either IP addresses or sending domains that have been previously identified as dangerous senders, usually through hitting spam traps or having high numbers of complaints.

Your content
Different ISPs look at the types of content that you’re sending in a variety of ways. Typically there are some key areas to watch out for:

Don’t link to websites that have been reported as sending spam in the past. Use a site such as to check this.
Ensure you’re not using link shorteners, as it will look like you’re trying to hide url’s.
Don’t send attachments, as these get flagged as dangerous, so link to them instead.
Some inboxes prefer you to have a 60/40 split of text to images. This doesn’t have to be exact; just make sure that you include some images and that they’re not touching each other in your html.

Lastly, ensure your unsubscribe link is clear and visible. There’s no point trying to stop people from unsubscribing, as all they’ll do is mark your sends as spam.

Your ESPs infrastructure
The last important factor is what Pure360 does for you. Our entire business depends on the successful delivery of large volumes of email. We have built a system that complies with the requirements of ISP best practice guidelines, giving you an extremely reliable platform for your email campaigns.

Your email will be authenticated with both DKIM and SPF technology. These tell the ISP that your mail has not been forged and is being sent from a verified source, Pure360. Compliance with DKIM and SPF positively marks your email in comparison to the spam that ISPs get from unauthenticated senders.

Depending on the amount of email that you send, Pure360 will make sure that your IP address setup is a perfect match for your sending pattern and volumes. As IP addresses are the main way that ISPs assign sending reputation, management of IP usage is important. Large volume email senders will have the benefit of sole responsibility over their own reputation by having a dedicated IP setup.

Pure360 are signed up for all ISP feedback loops, which allow us to easily unsubscribe your recipients who click the ‘mark as spam’ button. This helps you to avoid the spam folder because you are perceived as a sender whose mail is unwanted.

Five strategies for keeping your deliverability healthy

ISPs such as Gmail and Hotmail have various rules in place to encourage senders to follow best practice in their email marketing. What this means is that as long as you’re sending people the content that they’ve signed up to receive at the frequency they’ve requested, ISPs should recognise this in your results and your deliverability will improve as a result.

Maintain a healthy contact list
One of the biggest downfalls in terms of deliverability is to keep sending to people that are no longer engaging with your emails. Gmail and Hotmail will start to recognise this, and begin to assume that people don’t want to hear from you any more, sending your emails to junk as a result.

You can combat this by looking at the last open date that Pure360 stores against each of your contacts, and build a contact and re-engagement strategy around this.

If people haven’t opened an email for three months, set up an automation message with a different style of subject line that attempts to get them engaged in your sends again.

If people still haven’t opened for six months, then create a different contact strategy for them. A nice simple way is to create one segment for all your ‘engaged’ recipients and one for your ‘disengaged’. Send a few carefully chosen sections of content to all of your engaged subscribers once a week, and then at the end of the month chose the best performing ones from those sends and send these to the unengaged segment. That way the people that are engaged get lots of good relevant up to date information, but the ones that aren’t just get an occasional reminder that you’re still there with the very best performing content.

Be warned that old addresses will sometimes get recycled into spam traps, so all the old addresses that you keep emailing could end up doing serious damage to your deliverability.

If you have old data that has not been contacted for more than a year, to avoid this data impacting your positive active campaigning, separate your sending to these records by setting up a new profile and sender domain. Sending to unengaged contacts from the same domain alongside sending to highly engaged records can result in your engaged subscriber emails suffering from a reduced level of overall deliverability.

Also make sure your unsubscribe link is very clear on any sends you’re sending to unengaged data. If recipients can’t find it after a few moments, they’ll likely mark your email as spam and your deliverability will suffer as a result.

Set expectations of contact
Make sure you’re telling people at the point of signup what they’re going to be receiving and how often. This is the perfect way to ensure from the start of your relationship that they know what to expect from you. If you’re only going to send one newsletter a month, tell people so they’re expecting to hear from you. If you’re going to be sending the latest deals and offers from your website, tell them- then they won’t get any surprises and be tempted to mark you as spam.

Send a welcome email
While these also serve as a great opportunity to set expectations of contact, they can also be a great opportunity to start your relationship with your new subscribers on the best possible terms. Reinforce and remind people of all the great reasons why they signed up in the first place, tell them when to expect emails from you, or even tell them about your social channels so they can keep up to date with whats going on between your email campaigns and get them even more engaged with your brand.

Use a preference centre
The key with successful email marketing is giving people the type of content they want to receive to ensure they stay engaged, so let them tell you- set up a preference center with options for the type of updates they receive so it’s completely in your recipient’s hands.

Ensure recipients receive emails from the brand they signed up with
If they added their email address to and they start receiveing emails from, then they’re more likely to mark the email as spam and your sender reputation will suffer.

If you are sending on behalf of someone else, make sure it’s very clear on the signup form that this is what’s going to happen (setting expectations of contact), and on the email make sure you tell people “you signed up on but we said we’d send you a few related offers that we’ve carefully chosen. Please unsubscribe if you’ve changed your mind”.

What else can you do if you have a deliverability issue

If your emails are being sent to your recipients’ junk folder, or not being delivered at all, there’s plenty you can do to determine why this could be happening:

Start by using Pure360’s inbuilt deliverability checker, that can be found in the message editor once you’ve completed your content. This will give you a good indication if there’s anything content related that could be causing you problems.

Test your email to a different inbox. Even if Gmail isn’t accepting your emails, Hotmail may still be, so it’s helpful to know how widespread the issue is.

Try changing the subject line of your email to something completely different to see if this changes your results.

Swap the subject line of your email out with some safe plain text. You can generate some of this to use on sites like If this results in your email being delivered, it suggests there is a problem with your html. If your email is still having problems, it could mean there is a problem with your sender reputation.

Try comparing your campaign to a previous one that you know didn’t have any issues, and swapping in some of your new content with the old content to see if this affects results.

Make sure that your hard and soft bounce levels haven’t increased recently. If they have it’s possible that ISPs are viewing your sends as potentially dangerous.

If your sending volumes have increased recently it is possible that ISPs are rejecting some of the extra volume while they determine if your emails are safe.

If you are sending to purchased data or data that you’ve not contacted for a few months, you may need to re-engage recipients. Send them an opening email reminding them why they signed up and all the benefits of reading your emails.