Email deliverability guide
Understand email deliverability and its impact on sending emails.
Email deliverability refers to the ability of an email to successfully reach a recipient’s inbox, instead of being filtered into spam or rejected. The better deliverability a sender has, the more chance that their emails will stay out of the recipient’s spam folders.
Email delivery and email deliverability are often mistakenly used interchangeably, but they are two distinct concepts:
Email delivery is the number of emails delivered to the recipient server, regardless of where emails go after that.
Email deliverability focuses on what happens after delivery, measuring the ability to deliver an email to its intended placement in the recipient’s inbox.
Think of a package delivery service: a package addressed to your home could be marked as delivered, even if the package was left at your neighbor’s front door. Package deliverability would be poor in this case, as the package did not reach its intended address.
Why is email deliverability important?
As a business, understanding and monitoring your email deliverability is crucial as it directly influences the following:
Customer engagement: If your emails aren’t delivered to your customers' inboxes, you’re missing your opportunity to engage with your customers.
Reputation management: Your email domain can earn a poor reputation based on your deliverability rates, which can harm communication across your business. If you send too many emails that bounce or end up in spam, your domain will be flagged as an untrustworthy sender by email providers.
Email campaign ROI: When your team spends time reaching out to your customers via email, low deliverability means wasted effort and cost. Your audience can’t engage with your business if they don’t receive your emails.
What factors impact email deliverability?
There are several factors that determine email deliverability, working together to influence whether your email successfully reaches its intended place in the inbox:
Sender reputation
Email authentication
Email content hygiene
Recipient engagement and validity
Sender reputation
Sender reputation is one of the most critical factors for email deliverability. Internet Service Providers (ISPs) track and score email senders based on their sending habits. If a large number of your sent email bounces, or if too many recipients mark your emails as spam, your sender reputation will be negatively impacted. A poor sender reputation means that emails you send from your domain or IP address carry a high risk of landing in the spam folder or being rejected.
There are a few best practices for maintaining a positive sender reputation:
Warm up your sending domain gradually. A consistent and gradual increase in volume signals trustworthiness, whereas erratic sending patterns can be flagged by ISPs.
Regularly monitor your IP addresses to ensure they don’t appear on any blocklists.
Analyze and address email bounces promptly. High bounce rates can indicate that you’re sending emails to invalid or outdated addresses, which ISPs typically interpret negatively. Learn more about understanding email bounces.
Sign up for feedback loops from providers such as Yahoo and Gmail to get insights on which users mark your emails as spam. Use this data to adjust your email campaigns and reduce spam complaints.
We recommend the following tools to help you monitor your sender reputation:
Email authentication
Email authentication is a framework of protocols that are used to prevent spoofing. The protocols allow you to authenticate your emails so that ISPs can trust that emails sent from your domain are really coming from your company, and not someone pretending to be you. There are three common authentication protocols, and if any of these checks fail, your emails could be marked as spam or rejected by the recipient server:
SPF (Sender Policy Framework): SPF allows domain owners to specify which IP addresses are authorized to send emails on their behalf.
DKIM (DomainKeys Identified Mail): DKIM adds a digital signature to your emails that helps ISPs verify that the email wasn’t tampered with during transit.
DMARC (Domain-based Message Authentication, Reporting & Conformance): DMARC uses SPF and DKIM (both required for this protocol) by giving domain owners the ability to instruct ISPs what to do if authentication fails. A properly configured DMARC policy improves trustworthiness and protects against spoofing.
Attio is not an email service provider, but rather sends through your email service provider, which is either Google or Microsoft. Since Attio does not interact with recipient mail servers when sending your email, you do not need to authenticate Attio as an approved sender for your domain.
We do recommend authenticating through Gmail or Microsoft (whichever email provider you’ve synced), as their servers are ultimately responsible for sending and delivering email to your audience. We recommend ensuring SPF and DKIM, at a minimum, are enabled for your domain through your provider directly.
Note on DMARC: If you’d like to create a DMARC record for your domain, we recommend working with your domain or IT admin to do so. DMARC can harm deliverability if it’s set up incorrectly.
We recommend the following tools to help you check for the presence and validity of SPF, DKIM, and DMARC records on your domain:
Email content hygiene
Even with a strong sender reputation and proper email authentication in place, the content within your email can also significantly impact its deliverability. There are many pieces that factor into creating good email content that will stay out of spam. Here are some best practice guidelines:
Send content that is personalized and relevant to your audience. Use subject lines that are compelling to increase your open rate, and share content that is valuable to your audience to increase read time. Both of these factors work together to improve your sender credibility and audience engagement, and signal to ISPs that your email is not spam. Avoid re-using unsuccessful content.
Avoid spammy keywords and phrases. Using all caps, excessive punctuation (e.g., “!!!”), and spammy words like "free," "winner," “act now,” or "guarantee," can trigger spam filters. Overuse of such terms can lead to emails being flagged as promotional or malicious.
Use links sparingly. Including too many links, suspicious-looking URLs, or using links that follow redirects will raise spam flags. Links should match the sending domain wherever possible and should be used thoughtfully.
Avoid sending attachments, especially large ones. Sending large files or an excessive amount of attachments can make your email look spammy.
Maintain a healthy text-to-image ratio. Emails that contain a lot of images and little text are often associated with spam.
Ensure you use clean, simple code. Poorly coded HTML (e.g., broken tags or excessive use of formatting) can raise flags for spam filters.
Include a clear unsubscribe link in the footer of your email, making it simple for any recipient to unsubscribe from your communications. Unsubscribe links are automatically included in all emails sent from Attio sequences.
We recommend the following tools to test how spam filters may view the content of your emails:
Recipient engagement and validity
ISPs also track how recipients interact with your emails, making list quality another important factor for email deliverability. Keeping your contact lists clean and updated is one of the easiest ways to improve deliverability and engagement. When recipients consistently open and click on your emails, it indicates that your content is relevant and wanted, which in turn boosts your sender reputation.
Sending to outdated or unengaged recipients can hurt your sender reputation and lower engagement metrics. Here are a few best practices:
Verify that the email addresses you email are valid.
Avoid buying lists of email addresses, and regularly clean your list by removing inactive or bounced email addresses.
Avoid sending to consistently unengaged recipients.
Don’t resend emails to permanently bounced addresses.
Monitor your spam complaint and unsubscribe rate. High scores in these two areas signal to ISPs that your content is not relevant to your audience, which will lead to lower deliverability over time.
Use opt-in practices to ensure your audience is expecting to hear from you. Sending emails to people who didn’t explicitly sign up for your emails can lead to high spam complaints and low engagement.
We recommend the following tools to check the validity of email addresses in your list:
Attio’s deliverability protection features
Sequences were intentionally designed with deliverability in mind. We’ve placed the following safeguards in Attio to help prevent your emails from being caught up in spam, and to boost deliverability:
Any email that hard bounces will be automatically added to the Unsubscribes list
Unsubscribe links are required on all emails sent from Attio
Whether you're sending a single email, mass sending emails, or using a sequence, Attio uses email sending limits to space out email delivery