Email deliverability issues can be tricky to diagnose. For example, major mailbox providers, like Google and Apple, have robust spam filters that can prevent your emails from reaching subscriber inboxes. Your subscribers may not feel they’re receiving the emails they want and expect to receive from your brand. Or you may not have a sunset policy in place to ensure that you’re sending to subscribers based on their engagement with your emails.
In this article, we’ll list important signals that can help you monitor trends in email deliverability. We’ll also explore common issues that negatively affect email deliverability and how you can address them.
Monitor positive and negative deliverability signals
There are a number of signals that can help you monitor your email program’s success and identify potential problems.
Signals of positive deliverability
Signals that indicate successful email deliverability include the following:
- Opens
- Repeat opens
- Clicks
- Repeat clicks
- Website visits or app engagement
- Purchases/conversions
Signals of negative deliverability
Signals that indicate issues with deliverability include the following:
- Spam complaints: subscribers flagging your emails as unwanted or unsolicited
- Delivery to unengaged subscribers: delivery to email addresses that haven’t engaged with your emails in the past
- Delivery to subscribers unengaged with their own inbox: e.g., delivery to email addresses that have full inboxes or are over their quota
- Delivery to spam trap email addresses: includes subscribers who haven’t engaged in over six months and subscribers who never opted in to receive emails
- Delivery of content associated with higher rates of spam complaints: includes image-only emails, excessive white space, too many hyperlinks, and anything else mailbox providers associate with spam complaints
- Blocklist issues: e.g., IP or domain reputation issues
Address potential deliverability problems
When signals indicate there are issues with email deliverability, the cause almost always lies in one of three areas:
- How your relationship with subscribers began
- How you maintained your relationship with subscribers
- How your relationship with subscribers ended
Beginning of subscriber relationship
At the beginning of your relationship with the subscriber, we recommend addressing the following questions to ensure optimal deliverability:
- How do you collect email addresses? We recommend that subscribers actively opt in to receive emails from your brand. We also recommend designing your sign-up units so that potential subscribers know what kind of content to expect and how often they’ll receive emails.
- Do you send emails to any addresses that don’t have a direct relationship with your brand? We recommend that you never send emails to addresses that were purchased. And if you acquire a list, we also recommend that you clean the list to identify domain name typos, potential spam traps, etc.
- How long have you been collecting email addresses? If you’ve been collecting email addresses for more than a few months, we recommend monitoring subscriber engagement to ensure that you’re only sending to engaged subscribers.
Maintenance of subscriber relationship
After you've established a steady subscriber relationship, we recommend addressing the following questions to ensure optimal maintenance with your subscriber base:
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Do you send emails too frequently? Pay particular attention to how frequently you send emails to subscribers who aren’t opening them. Every brand has to find the “right” frequency for their subscribers. We recommend testing several different frequencies to find which is the most effective. You should also be sure to reduce the frequency of emails to subscribers who don’t engage with your emails early in the subscriber journey.
Because mailing frequency is an important component of email deliverability, you should set (then adhere to) mailing frequency expectations when subscribers opt in to receive emails. Carefully consider changes in these frequencies, especially around the holidays. For example, if you plan to send extra emails for Black Friday and Cyber Monday, you should slowly increase your sending frequency over the course of a few weeks. - Do you send emails consistently? Mailbox providers are less likely to flag your emails as spam when there are consistent sending patterns and volumes. Fluctuations in patterns and volumes can cause deliverability issues.
- Do you see high rates of bounced emails or addresses with full inboxes? These are both signs that you need to clean your email list.
- Do you see delivery issues with seed addresses? Seed addresses are email addresses that you create to test and monitor email deliverability. Brands often create seed addresses for all of the major inbox providers (Apple, Google, Microsoft, and Verizon Media Group). Keep in mind that if you’re seeing issues with seed addresses, they may not necessarily indicate a wider issue, since some mailbox providers identify seed addresses and will treat them differently than actual subscriber email addresses.
- Do your emails contain URLs with third-party domains? If you have URLs that link to third-party domains, and those domains have reputation issues, then you could see issues with email deliverability. In particular, services like URL shorteners (e.g., bit.ly) and image hosting sites are often abused by spammers and are likely to have reputation issues. We recommend that you avoid using these services whenever possible.
- Are the emails you’re sending relevant and engaging? Relevant emails are those your subscribers want and expect to receive. You can make it clear when subscribers opt in what kinds of emails they'll receive and how often. Generally, you shouldn't send emails more than once a week, and you shouldn't use them to make unrelated announcements.
Engaging emails use industry best practices to keep subscribers engaged. For more about sending relevant and engaging emails, see Deliverability best practices.
Ending of subscriber relationship
When subscribers unsubscribe from your emails, we recommend asking yourself the following questions to ensure effective transitions and future opportunities for remarketing:
- Are unsubscribe requests honored? It’s important to ensure that when subscribers unsubscribe from your emails, they’re removed from your list. Otherwise, they’re more likely to report your emails as spam.
- Do you have a sunset policy? A sunset policy is a segmentation strategy to identify unengaged subscribers so that you can adjust how frequently you send emails to them or remove them from your list altogether. We recommend suppressing email addresses from your list that no longer show positive engagement. The amount of time before you suppress email addresses can vary, but in any case, you shouldn’t send emails to subscribers who haven’t engaged with your messages for more than 6–12 months.
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