In the world of email, the journey from crafting your message to reaching your recipient's inbox involves a series of intricate steps. As a sender utilizing an Email Service Provider (ESP) like SendGrid, it's essential to grasp the complexity of this process. Let's take a closer look at the lifecycle of an email and the key checkpoints that can significantly impact its delivery.
It all begins with the creation of your message. Whether it's a promotional offer, a newsletter, or an important update, your content sets the stage for the interaction between your business and your recipients. Once your content is ready, you pass it to SendGrid through our API, where the magic and complexity begins.
SendGrid initiates a series of authentication checks, starting with validating your credentials (username, password, or API key) to ensure you have the right to send emails through our platform. SendGrid then check for your sender authentication records – SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance) – which will then be added to the outbound message. These records act as a roadmap, guiding your email through the intricacies of the email’s journey.
Although there is other content that may be added or checked by SendGrid depending on various features and specific use cases, this blog focuses on the general path your email is taking. For example, if you’re relying on SendGrid to manage your unsubscribes, we may add the link to your email, or if an address is on a Suppressions list, the email may be dropped.
NOTE: In early 2024, Gmail and Yahoo increased the requirements on high volume senders to have improved authentication, one click unsubscribe enforcement, and reduced spam reports. To best prepare our customers, SendGrid will be offering a DMARC policy for all new Sender Authentications as well as adding one click unsubscribe for all subscription management options. Read our blog: Gmail & Yahoo Sender Requirements for more information.
Once an email passes authentication checks, SendGrid proceeds to establish a connection with the recipient's mail server. The steps are as follows:
SendGrid attempts to connect to the recipient's mail server.
The sender waits for a response from the recipient's server. A successful connection will return a 200 OK response. A rejection can also occur at this stage. The connection could be rejected due to reasons such as poor IP/domain reputation or too many simultaneous connections from the sender.
If the connection is accepted, the sender must identify itself with the reverse DNS (rDNS) and the connecting IP address to verify the sender’s identity. This would be SendGrid’s default records, or your customer records if they have been set up.
The recipient's server then validates and checks the details of the message, including the recipient's email address, to ensure it is valid and able to receive emails.
Upon reaching the recipient server, your email undergoes another round of scrutiny from their spam filters. These filters consider various factors, including sender reputation, content analysis, and adherence to authentication protocols. It may either accept your email for delivery or, in some cases, reject it for reasons such as suspicious content, blocklisted sender, or failed authentication.
For example, if you have a DMARC policy that is set to reject email if SPF and/or DKIM authentication checks fail, your email may be rejected. Regardless of the decision, the receiving mail server will almost always respond with a reason, with the level of detail in the response depending on the specific recipient server (Gmail response for an invalid email address may differ that Yahoo’s).
Sending from a domain or IP address that is listed on a 3rd party blocklisting service like Spamhaus and SpamCop can also influence what happens to your email. However, there are hundreds of blocklisting services with each having various levels of impact and listing criteria. If you want to know more, please read our blog: Avoiding Email Blacklists.
When an email is accepted for delivery, the placement of that email is up to the recipient server/mailbox provider, based on the factors mentioned above. They can decide to put it in the inbox, spam folder, or quarantine the message entirely. SendGrid is generally unable to verify what specifically happens to a message after it has been accepted for delivery, so troubleshooting these scenarios often requires reaching out to the mailbox provider for additional information.
In the event of rejection, often referred to as a block or bounce, SendGrid will handle the email based on the recipient server response. If the message was rejected because the email address is invalid or doesn’t exist, the email address is added to a suppression list which you can use to help manage and update your contact list. The rejection may also be temporary, like sending too much mail too quickly or a server connection issue, in which case SendGrid may queue the email and reattempt delivery.
Sendgrid helps manage the millions of block/bounce reasons with 7 classifications; Invalid Address, Technical, Content, Reputation, Frequency/Volume, Mailbox Unavailable, and Unclassified. You can read more about Bounce Classifications here.
Email delivery is a complex expedition with multiple checkpoints. SendGrid provides tracking and analytics data for monitoring email delivery, open rates, click-through rates, block/bounce reasons, and other metrics that help you refine your email strategies.
Understanding each step empowers you to navigate potential hurdles, optimize your email campaigns, and ensure your messages reach the intended audience. The next time you hit send, know that your email is embarking on a fascinating expedition across the digital sea to connect with your recipients.
