Issue
Users may see some sent email marked as Delivered in SendGrid that never arrives in the recipient's primary inbox. This is often the result of the recipient server accepting mail for delivery, but then sorting the mail into another folder (or tabs if using Gmail). This guide explains why this may occur, and tips for avoiding this issue in your future mail sends.
Product
Twilio SendGrid Email
Cause
Twilio SendGrid posts the Delivered event after the recipient server accepts the message with a 250 OK response. At this point, the receiving server could send your mail to the inbox, queue it for later delivery, route it to a spam folder, filter it to a security quarantine, or even drop the email entirely.
Post-acceptance filtering occurs when the receiving server accepts a message for delivery before running additional security checks. While most legitimate email reaches the intended inbox, the receiving server can route your message directly to a spam or junk folder. In enterprise environments, messages are frequently intercepted by email security appliances or gateways (such as Proofpoint or Mimecast) and sent to an administrative quarantine—which often explains why an email is marked "delivered" but seemingly disappears. In rare cases, the receiving server may choose to drop (delete) the message altogether.
In all of these scenarios, SendGrid is only notified of the initial email acceptance and thus posts the Delivered event, leaving no visibility into downstream filtering. Any additional SendGrid events for your message would be triggered solely by recipient engagement (such as open/click events, unsubscribes, or spam reports).
Resolution
Sender Authentication and Good Email Practices
It is definitely frustrating when your mail ends up outside of your recipient's primary inbox. There are many reasons why mail might be sorted outside of the inbox. Inbox service providers (ISPs) will check for the reputation of your sending domain. If the recipients have reacted well to mail from a particular domain, then email from that domain will most likely land in the inbox. On the other hand, a good email sent from a domain with an uncertain reputation would most likely land in spam or elsewhere.
Your sending IP should be properly warmed up and authenticated for your sending domain. It is highly recommended not to mix marketing with transactional mail over the same sending IP as marketing emails generally trigger a higher spam report rate.
Additionally, you should authenticate the domains you are sending from. In order to show the ISPs that you are the sender and that you meant to send these messages, you must properly authenticate your mail. The domain needs to be authenticated so that the SPF and DKIM "pass" and recipient servers see that SendGrid is authorized to send mail on behalf of your domain. It is also highly recommended to brand your links - the links should be from your own domain and they shouldn't be blacklisted.
If the above guidelines are met (the sending domain matches the domain authentication and is properly done, the content is relevant and not associated with unwanted mail, and the IP is properly warmed up) the emails should start delivering to the inbox.
This, however, will not happen overnight. It can take ISPs 3-4 weeks to adjust the reputation for the sending IP or for a new domain. It can sometimes take 3+ months to change the reputation of a domain that they know has a history of bad sending practices.
Mail delivered to Gmail Tabs
Since its creation, the tab system within Gmail has offered its users the ability to further segment their inboxes based on these types of messages: Primary, Transactions, Updates (News, Subscriptions and Social), and Promotions. In particular, the Promotions tab has been a popular topic of discussion with our customers.
The Gmail tab system is a segmented way to view the inbox within Gmail. A user who does not have tabs enabled will see your messages in their inbox as normal. Emails that end up in a tab are not being filtered like a message that ends up in a spam folder, they are in fact being assigned to a different section of that recipient's inbox.
Messages that are sent to multiple recipients, especially those that include special offers or time-sensitive deals, are much more likely to end up in the Promotions tab. This is what the Promotions tab was designed for, and ultimately your recipients control which messages end up in that tab versus their Primary tab. You can also view this great resource that specifically addresses getting mail out of the Promotions tab.
Additional Information
It is also recommended to be sure that you are following SendGrid's recommended practices. You can check out the 2026 Deliverability Guide for great information on how to achieve optimum deliverability.
It will take some time for your mail to start being delivered directly to your customers’ inboxes, but following the recommendations above is the best way to avoid your mail being sorted elsewhere. If you need additional assistance with delivery, you can also contact our Deliverability Consulting team. You can find more details on our Expert Services page.