Twilio SendGrid Support Deliverability Guide

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:
  • Sometimes the authentication fails after you added the DNS records. If so, please keep in mind the TTL, and wait for that period before trying to validate your domain again. 
  • Enter your domain name without www or http/https
  • We generate the records required for Domain Authentication as they must resolve, not as they must be entered into the DNS settings. For example, if our system generates something like, and your DNS hosting (for example, GoDaddy) adds your domain name automatically at the end, you should enter em3180 only in the Host field of the record. 

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 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:
  • Single Senders do not have associated SPF or DKIM records.
  • We do not recommend using Single Senders for API/SMTP sending
  • Although Single Senders are used mostly for Marketing Campaigns, if you have authenticated the sender domain, you can use it without having to authenticate a Single Sender email address.
  • Single Senders are used for testing purposes, mostly. 
  • Single Senders must be able to log into the SendGrid account to verify. 

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 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:
  •  Without Link Branding, a link with Click tracking enabled would look like “”. With Link Branding configured, it would show up as “" 
  • SendGrid uses http:// by default when using Link Branding. If clicking a branded link leads to a security error, while having Link Branding and Click Tracking enabled at the same time, we recommend following the steps to enable SSL Click Tracking. Additional information is available here: Setup SSL for Click tracking

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:
  • If you see a considerable amount of Deferrals or Bounces when sending from a dedicated IP without rDNS, try setting it up.  
  • If you use multiple sender domains in your account, with only one dedicated IP, we recommend setting up rDNS for the domain that sends the highest volume of emails.


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:

How to implement DMARC

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:

Additional information about some of those services can be found in 5 Ways to Check Your Sending Reputation

To keep in mind:
  • Several email or email security providers have their own ways to measure Domain/IP reputation, so the results from the sites above are used mostly for guidance. 
  • If your sending IP(s) are blocklisted, check first if the blocklist caused message rejection. Smaller blocklists do not affect your overall deliverability as not many email services use them. 
  • More information on Blocklisting and how to avoid it is available in this blog article

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.

1. CAN-SPAM compliance

2. Sender reputation

3. List cleanliness/sending to spam traps

4. Spammy subject lines

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 Practical tips for senders of e-mails

To keep in mind:
  • A delivery event is registered with SendGrid when the recipient server takes the email payload from us. After that point, it is like handing off an envelope to the postal worker. You may get a confirmation of delivery, but you won’t always know where the mail was finally delivered to.
  • Only messages manually marked as Spam by the recipient appear in the Spam Report Suppression List. Emails marked as Spam by the server on the recipient side appear as “Delivered” to us, which is why diagnosing Spam classification reasons is better done with the email team on the recipient’s side. 
  • What to check how “Spammy” your messages are before sending them? Use our Email Testing feature or third party services, like Mail Tester
  • Want further advice on preventing Spam blocking? Take a look at our article on Recommendations and Best Practices to avoid Spam Blocking

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: 

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

Google Postmaster Tools

Sender Contact Form

2. Microsoft (,,, 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 and contact form for Microsoft Office 365

3. Yahoo (includes and

Complaint Feedback Loop

Sender Support Request

4. Comcast

Complaint Feedback Loop

Comcast Postmaster

5. Apple

Doesn’t offer a Feedback Loop

Email 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

Dynamic reputation IP lookup

CSI IP Reputation Remediation Portal


Doesn’t provide a feedback loop

Postmaster Contact Form or email

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

Unable to Send Email to Gmail

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

Avoiding Spam traps

DNS Validation records when using Cloudflare

Activate Unsubscribe Links

Email Delivery Deferrals

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

What is a Suppression List

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 Email Delivery Requirements


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