Deliverability best practices - how to keep my email from going to the SPAM folder

Watch a short webinar: Contacts Cleanup

Managing your contacts can be a daunting task, but there are some best practices and resources that can help! rezora has some great tools for identifying active and inactive contacts, and with some small changes you can start seeing higher open rates, and more of your emails going to the Inbox. This webinar will have a quick 20 minute presentation, followed by a 10 minute open Q&A.

We've put together a comprehensive list of the best practices you should be focusing on when considering deliverability. Please see this link here for the full document.


rezora Deliverability Resource

What can cause an email to go to SPAM:

Deliverability in digital marketing is key -- by this we mean taking steps to help your email reach the inbox of your recipient. When you send a contact an email, their email server performs quite a few ‘checks’, and makes the decision on how to receive that email. It’s important to know that it’s not always a simple pass/fail -- I’m sure we’ve all seen some examples of this before. For example an email might go to the inbox, but with some content blocked (requiring permission to download images, etc.). An email might be diverted to SPAM, or could even be refused completely (this is called a ‘bounce’).

Since each email server uses its own criteria and process, it can sometimes be tricky to pinpoint exactly why an email went to SPAM. However there are many things you can do as a digital marketer to ensure the best deliverability possible. We’ve compiled a list of the biggest factors, and the best practices that you can adopt to see the best deliverability (and open rate) possible.


One of the ‘checks’ that receiving email servers perform will be to authenticate your email -- is the sender who they say they are? This is done primarily to prevent phishing and spoofing, which is when a sender purposely misrepresents their identity. Usually this is done by making the email seem like it’s coming from a reputable sender, when it’s actually coming from a different source. Phishing is very often done to attempt to ‘smuggle-in’ malicious content or code.

Did the sending IP Address have permission to send on behalf of that domain?

The email server of each of your recipients will check with the from address’ domain, and check to see if rezora has permission to email on its behalf. The best way to ensure that this authentication is successful is to use your company-provided email address specifically. This is really important! Your company email address has good settings in place to ensure that your emails are properly authenticated, and you’ll see the best results using that address.


One of the most important things to consider is your content! Good content design is vital in marketing, but it’s also a factor in deliverability:

How many images do I have in my marketing piece, and how big are they?

When an email server scans an incoming email, it can only scan text-based info -- they can’t scan images very well, other than to see where that image is located (filepath). When an email contains mostly image content, or if the content is one big image, it registers as an email with mostly unscannable content. Since the email server can’t effectively scan the content, it will often block content or send the email to SPAM.

What does this mean for your marketing pieces?

The best advice is to ensure that each image is under 1 MB in filesize, and to make sure you include a good mix of text content with your images. If you’re not sure how big your images are, a good practice to be in is to scale your images down to roughly 600-800 px wide. Nowadays it’s pretty common for images to be very large, but in an email environment an 800 px wide image will look great!

Does your email body or subject line use any “spammy” keywords?

The text you choose for your email is important! This is especially important for your subject line - for best results, you should use all proper case (no caps!), and avoid using any special characters. Avoid “spammy” keywords like “Click here”, “Opt in”, “Guarantee”, “Act Now!”, etc. Pay attention to your links Make sure they’re legitimate, and make sure they work by clicking on each of the links in your test email.

Avoid embedding videos

Most email clients do not support videos, and including one in your content is likely to land your email in SPAM. Instead of embedding a video, insert an image of the video, and hyperlink it to the site where the video is hosted. This will help your email reach the inbox, and ensure that all recipients can see your content.

Don’t copy and paste large amount of text/images When you copy content from an online source, more than just the text/images is copied! It also copies all the code you selected, including any non-readable characters. This can cause odd alignment issues, but it’s also something that can raise red flags in an email client.


One of the most overlooked factors is your contacts themselves! Contact management and sending practices are a big factor in your personal reputation online, and each contact may have individual settings in place affecting how emails are delivered to them.

Are your contacts expecting your emails?

This may sound like an odd question, but it’s really important! Did each of your contacts signup to receive your emails? With GDPR now in effect, it’s more important than ever to make sure that you have a record of when that contact signed up for your emails, but it can also be a factor in deliverability! When a new contact signs-up for your marketing, it’s a good idea to ask them to add you as a contact in their email account. If they add your email address in their own account as a contact, it will let their email server know that they are expecting your emails, and it will “grade” your emails more leniently.

One good trick: when you get a new contact, send them a welcome email! Don’t use bought lists! Unless, that is, you want to ruin your reputation as a sender. These lists will very often contain undeliverable email addresses that will tell email providers you’re sending unsolicited messages, almost guaranteeing you a spot on the spam list. These are called “spam traps”. The list of reasons to avoid bought lists could go on, but ultimately they aren’t effective, aren’t permitted in rezora, and can hurt you and your team’s reputation.

Has a contact engaged in your emails in the last six months?

Don’t send to stale contacts!

One of the great things about rezora is the instant analytics you receive for your contacts -- if you see a contact hasn’t clicked on a single email you’ve sent them within, let’s say, 6 months- delete them from the list you’re sending to and move on. This will go a long way to protecting your sending reputation.


One of the most important factors in digital marketing is reputation. The receiving email server will check the online reputation of the ‘From’ email address (e.g. agent@companywebsite. com), the address’ domain (e.g., and the sending IP address (rezora’s).

The internet community keeps track anytime someone marks an email as SPAM, or if a particular domain or IP address have lots of bounces, and will influence how future emails are delivered as a result.

What is the online reputation of the ‘From’ domain -- is it known for sending SPAM?

As you send emails on behalf of your company domain, the online community will “keep track” of the results. Fewer bounces lead to better and better results, and more bounces or reports of spam can have adverse effects. What is the online reputation of the sending IP Address (rezora’s) - is it known for sending SPAM?

Here at rezora, we go to great lengths to protect the online reputation of our sending IP addresses. Our developers monitor for issues, and quickly take action if we spot anything amiss. We maintain a bounce list to prevent unchecked repeat bounces, and help our users increase deliverability through our support team. What is the online reputation of that ‘From’ Address - is it know for sending SPAM? The internet will remember your sending practices too! As you send marketing pieces, do everything you can to prevent it from going to SPAM, and your email address will become known in the community as ‘reputable’.


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