This deliverability overview guide is intended to encompass most aspects of deliverability when sending emails. The topic is extensive, so each section is intended to be a simplified overview. However, the resources linked here will lead you to more in-depth articles and supplementary information.
'What is email deliverability?' and Other General Resources
Email deliverability refers to the ability of your emails to reach your recipients’ inboxes. Good deliverability means your emails are arriving in inboxes as intended, while poor deliverability means your emails could be filtered to spam, or blocked by the recipient servers.
As a starting point, it is highly recommended to take a look at SendGrid’s 2023 Email Deliverability Guide. The deliverability guide contains valuable industry knowledge that can be used by new and veteran senders alike, which can help to improve your overall deliverability and get you into the inbox. You can also refer to SendGrid's Best Practices article, for the distilled practices of good deliverability.
Since deliverability and its related issues are rather vast, it may also be advised to review for common delivery failures and their fixes first before diving into deliverability itself: Email Delivery Failure: 11 Common Causes (& How to Fix Them)
Best Practices
When it comes to deliverability best practices it is important to note that they are more of a guideline to follow, as there is no guaranteed fix for delivery issues. Although there is no one-size-fits-all solution, there are many factors that you can use to influence deliverability. Much of deliverability depends on sender behavior and in some cases, that of other SendGrid customers (for plans which use Shared IPs). Below you can find some best practices you can implement in your sending to prevent, monitor and correct delivery issues.
1. Email Authentication
Email authentication gives confidence to email providers that messages are not sent fro bad actors. The higher the confidence, the higher the probability of messages being delivered to the inbox. There are many aspects to email authentication, some directly related to your SendGrid setup, some related to your domain, which we mention below.
Sender Authentication
Sender Authentication is Twilio SendGrid’s own terminology for providing authorization to SendGrid to send emails on your behalf. As a third party email provider, SendGrid must be able to show that it is permitted to relay emails on a sender’s behalf, and these methods are how that authorization is presented to recipient servers for verification. Any domain that you are going to send emails from, should be authenticated through as many of these means as possible for the best delivery experience. The following are the authentication methods available in SendGrid.
Domain Authentication
Domain authentication is a process that verifies the legitimacy and authorization of your domain in email communications. When your domain is authenticated in your SendGrid account, it allows us to send emails on behalf of your domain. This process implements SPF and DKIM records, which are two critical standards that recipient servers look for when evaluating if your emails are legitimate and safe to deliver to recipients. Without domain authentication, your emails are more likely to be filtered to spam or blocked.
You can find more information on how to authenticate your domain in SendGrid here: How to Set Up Domain Authentication
Note: If the Domain Authentication fails, you can refer to this troubleshooting guide.
To keep in mind:
|
Single Sender
If you do not own a domain or cannot own a domain, but need to use a specific email address as From: or Reply-to: (for example a @gmail.com address), you can authenticate the address via Single Sender verification. This authentication method is required for Marketing Campaigns as well. This article shows the steps for Single Sender Verification.
To keep in mind:
|
Link Branding
Spam filters and recipient servers look at the links within emails to determine whether the email looks trustworthy. They use the reputation of the root domain to determine whether the links can be trusted.
By default, link and image URLs, are served by sendgrid.net. Link Branding allows your domain to show up on those URLs instead. Implementing this feature helps in email deliverability because you are no longer relying on click tracking pointing to us, it helps create a consistent online presence and can help improve your site’s ranking in search engines.
To set this up, we recommend following the steps at: How to set up Link Branding
To keep in mind:
|
Reverse DNS (rDNS) [For dedicated IP users only]
When you are in a plan with includes dedicated IPs (Email API Pro/Enterprise, Marketing Campaigns Advanced), linking your dedicated IP to your sending domain, provides an additional layer of authentication to your outbound emails and reinforce brand recognition. While it is possible to send mail without rDNS in place, missing rDNS means that you are using generic A records which do not help delivery in the best cases, and hinder it in the worst cases. The article on How to set up reverse DNS will help you with this.
To keep in mind:
|
DMARC and BIMI
These authentication initiatives are not directly related to your SendGrid account but your domain and they are highly recommended to improve email deliverability. While DMARC aims to prevent spoofing, BIMI provides an additional layer of Brand recognition and might improve deliverability to those email providers that have implemented that standard (like Yahoo, Gmail and Apple Mail). Although we do not provide support setting them up, you can refer to the following resources in that regard:
SendGrid and the BIMI initiative
2. Proactive Monitoring of Sender Reputation
Deliverability is largely reliant on sorting rules and requirements of the recipient server and if the practices and reputation of the sender meets their criteria for inbox delivery.
Typically, recipient mail servers look at your IP traffic, reputation, and content in order to determine where your mail should go. Recency and quality of sender metrics also play a large part in accruing and maintaining a great reputation that will reflect in deliverability results. Most of all, email content is something that should also be curated according to delivery guidelines and recommendations for the best results.
Since Sender reputation refers both to the Domain used for sending purposes, and the IP from which emails are sent, it is important to know the different between them. For that, you can refer to Email Sending Reputation 101: IP Reputation vs. Domain Reputation
Although SendGrid offers a reputation measure, it is internal to SendGrid, and it doesn’t represent your reputation with other mail or email security providers. For that reason, we recommend using third party services, which will analyze the reputation of your IP and your Domain as well, like:
- SenderScore
- Barracuda Central
- Customer URL Ticketing System from McAfee
- Talos Intelligence by Cisco
Additional information about some of those services can be found in 5 Ways to Check Your Sending Reputation
To keep in mind:
|
3. Opt-in/Opt-out
Focus on acquiring subscribers who are genuinely interested in your content or products. Always obtain explicit permission from subscribers before adding them to your email list. If you’re looking to go the extra mile, you can implement a double opt-in process, where subscribers confirm their intent to join your mailing list by clicking on a verification link sent to their email. The different consent types and information on how to build a strong contact list is available in this guide: How to Build an Email List From Scratch (the Right Way) in 2023
Make it easy for customers to unsubscribe from your emails when they no longer want to receive them. If your unsubscribe options are too difficult to find, or they continue to receive emails after submitting a request to unsubscribe, they are likely to report your emails as spam. Spam reports, in turn, can have a serious negative impact on your sending reputation and deliverability. Visit our blog post on Email Unsubscribe Best practices.
Twilio SendGrid helps to make managing your email list and managing your unsubscribes easier. For further compliance and technical information, you can refer to:
|
To keep in mind: Unsubscribes are a normal part of the communication between senders and recipients, but if you notice a high rate of them (above 1%), you can take a look at our blog article: How to Remedy a High Email Unsubscribe Rate |
4. Spam tracking and control
While there are many reasons your email could be landing in the spam folder, the 5 most common reasons they’re ending up in spam are mentioned below. It could be one or a combination of these, so it is important to ensure that each of these is paid due attention to remain compliant with best practices and industry standards for sending emails.
2. Sender reputation
3. List cleanliness/sending to spam traps
5. Too many attachments
A summary of those items is available at Why Are My Emails Going To Spam?
To prevent your mass emails from being marked as Spam, we recommend always following the Bulk sender guidelines specific to different email providers. Here is a quick list:
Google: Email Sender Guidelines and Bulk email best practices
Microsoft: Improving E-mail Deliverability into Windows Live Hotmail and Troubleshooting mail sent to Microsoft 365
Yahoo: Sender Best Practices
Comcast: Deliverability Best practices
Apple: Postmaster information for iCloud Mail
Yandex: Yandex deliverability best practices
Proofpoint/Cloudmark: Best practices and troubleshooting tips
T-Online.de: Practical tips for senders of e-mails
To keep in mind:
|
If you are seeing an increase in spam classification for your outbound messages, we have tips and resources to stop your emails from going to spam here: Top 10 Tips and Tricks to Stay Out of the Spam Folder
5. Monitoring Blocks and Bounces
Although SendGrid provides Delivery Stats and other reporting options, a really great (and recommended) way to monitor blocks and bounces almost in real time, is by setting up an Event Webhook.
Each event typically comes with a reason response header from the recipient server that will either explain why the email was rejected or point you toward where the issue really lies according to the recipient server.
If you believe a Webhook is not a suitable option for your organization, you can still use our reporting tools. As a starting points, you can take a look at our Deliverability Insights located under the Stats section of the UI, and in particular, its Bounced & Blocked tab. We also advise you to take a look our article on Bounce Management.
|
To keep in mind: Blocks are bounces are not always caused by you or your sending behaviors. Sometimes recipient servers are just experiencing a temporary outage. In any case, we recommend this troubleshooter if you see many bounced/blocked messages: What to do if my email messages are blocked |
6. Keep a clean contact list
Sending emails only to those who actually want to read them is the best way to maintain good sender reputation, reduce spam classification or blocking and improve your engagement rates. We offer the Email Address Validation tool to check if new email addresses are valid, but there are other online resources for that purpose. Take a look at our 5 tips for email contact hygiene for further information.
|
To keep in mind: Clearing up the contacts in the Suppression Lists, do not remove the contacts from the Global Contact List. If you clear those lists, you might end up, inadvertently, sending emails to an invalid address, one that marked your email as Spam in the past or one that Unsubscribe. For that reason, if you have confirmed that those email addresses don’t want or cannot get your emails, you can remove them in bulk from your contact list, as explained in our support article about Contact Management |
7. Send emails that people want to receive and keep your contacts engaged
Engagement refers to how recipients interact with your emails after it is delivered, not only by opening the email but clicking its links. Repeated engagement – where a subscriber opens emails from a sender on an ongoing basis – is a strong signal of wanted mail, and maintaining strong performance in this area will always benefit deliverability.
To keep an eye on your Engagement Quality, we have launched a new API which provides a score for your account, based on Engagement recency, Unique open rates, Bounce rates, Bounce classification and Spam rate. Information on how SEQ works and how to use the API is available in SendGrid Engagement Quality API.
For more information, check 9 Strategies to Increase Email Engagement and How to Create Effective Re-Engagement Email Campaigns
Sunsetting contacts that aren’t engaging with your emails will improve overall engagement, and help to show inbox providers that recipients want your emails. More information on how to set up a sunset policy for unengaged recipients here: https://sendgrid.com/blog/building-your-business-case-for-an-email-sunset-policy/
Need inspiration to keep your customers engaged? Take a look at our guide
Additional Information
1a. For Plans which use Shared IPs
Free plans, Email API Essentials and Marketing Campaigns Basic, use Shared IPs. Although it has advantages, particularly when the sending volume is low (because the IPs in use are always warm), it also has its drawbacks, as the reputation of those IPs not only depend on your behavior but that of other SendGrid customers using the same IPs.
While we do our best to keep our IPs in good standing, some email services do not provide feedback regarding which particular account sent too many emails, or Spam messages, so sometimes the shared IPs get blacklisted by no fault of your own.
To tackle this issue, Twilio SendGrid has a new and improved shared pool experience that assesses customer sending behavior by advanced performance statistics. The better your particular sending behavior is, the higher the chance of being group with likewise customers and therefore, to increase your deliverability. For more information on those Pool improvements, take a look at our Blog article.
For a more in-depth view of best practices for accounts which use Shared IPs, we strongly recommend our Email Deliverability: Shared IP Pools 101 article.
1b. For plans which use Dedicated IPs
Warming up your new dedicated IP is the best way to build a good reputation with ISP and email providers alike. One of the most common reasons for delivery issues is immediately sending out high volumes of email before the IP has been introduced to recipients or had reputation established. Warming an IP address is very critical for high volume senders and marketing senders primarily. For information on how to go about it, visit our IP Warm Up Guide.
Additionally, major email providers like Google, Microsoft, and Yahoo provide tools to analyze your email performance and provide feedback regarding Spam reports and general information about their bulk sender policies.
1. Google
2. Microsoft (Outlook.com, Hotmail.com, Live.com, MSN.com and Office 365)
Smart Network Data Service. You can also check What Is Microsoft Smart Network Data Services (SNDS) and Do I Need It?
Contact Form for Outlook.com and contact form for Microsoft Office 365
3. Yahoo (includes Verizon.net and AOL.com)
4. Comcast
5. Apple
Doesn’t offer a Feedback Loop
Email icloudadmin@apple.com to request assistance with deliverability to iCloud-related recipients
6. Yandex
Link to Feedback loop doesn’t work at the moment.
Contacting Yandex Mail support
7. Proofpoint/Cloudmark
CSI IP Reputation Remediation Portal
8. T-Online.de
Doesn’t provide a feedback loop
Postmaster Contact Form or email tosa@rx.t-online.de
Since customers with dedicated IPs have full control over their reputation, if you notice any blacklisting, the delisting request must be sent by you directly. Links to delisting requests forms for other email providers are available in this support article.
Contacting SendGrid Support
When contacting our Support team to troubleshoot delivery issues, providing specific examples (From, To, sending time), email headers (if messages are not passing authentication or are being classified as Spam) and a clear description of the issues you are experiencing (when it started, which rejection message you get, etc.) will help us investigate delivery issues faster.
Please keep in mind our Support policies and scope of support, since some delivery issues are caused by policies on the recipient’s side that we cannot address directly. Nevertheless, we will always do our best to point you in the right direction.
Expert Services
Beyond the general recommendations and best practices, if you need something that goes a bit further than what the tech support team offers, you may be interested in hiring Expert Services Consultants: Expert Services Deliverability Help.
Specialized Troubleshooting Guides
Troubleshooting Email Messages Marked "Delivered", But Not Appearing in Inbox
Troubleshooting Twilio SendGrid email delivery delays and latency
Sender Policy Framework (SPF) DNS lookup limitations
Use a Custom DKIM Selector for Authenticating a Single Domain on Multiple Accounts
Troubleshooting Email Delivery Failures due to DMARC
DNS Validation records when using Cloudflare
What Are Email Blocklists (and How to Avoid Them)
Further Resources on Deliverability
Twilio SendGrid Email Prohibited Content Types and Uses
Email Deliverability 101 for Email Marketers
8+ Best Practices to Improve Your Email Deliverability
Gmail’s Blue Verified Checkmark: A New BIMI Incentive
Avoiding the Gmail Promotional Tab
The Essential Guide to Email Segmentation
8 Email Metrics You Need to Keep Your Eye On
12+ Email Marketing Strategies for Engaging Campaigns (2023)
Email Deliverability: 6 Common Email Myths Debunked
How to Meet the New t-online.de Email Delivery Requirements