Why are emails delayed when sent from Marketing Cloud on a shared IP despite proper authentication?

Email marketer from StackExchange explains that when using a shared IP address and a shared hosting provider, there could be an issue in the configuration, or the hosting provider's IP address may already be blacklisted from sending spam emails. Thus, your authenticated emails may be delayed or never delivered at all.

Email marketer from Neil Patel Blog explains that using a shared IP address for email marketing can lead to deliverability issues, even with proper authentication, because your email reputation is tied to other users on that IP. If they send spam or have poor email practices, it can negatively affect your deliverability.

Email marketer from Mailjet Blog shares that with shared IPs, you're relying on the good sending behavior of other users on the same IP. If one user sends spam, it impacts everyone, potentially causing delays even with proper authentication.

Email marketer from Reddit shares that even with proper authentication, Marketing Cloud emails on a shared IP can be delayed due to SFMC's infrastructure, shared IP reputation, or the recipient's mail server load. Some ISPs have aggressive throttling policies on shared IPs.

Email marketer from Email on Acid Blog shares that several factors can affect email delivery time, including the sender's reputation, email content, recipient's email client, and network conditions. Delays can occur even with proper authentication if the content triggers spam filters or the recipient's mail server is experiencing issues.

Email marketer from Litmus Blog answers that a poor IP reputation, even when using proper authentication (SPF, DKIM, DMARC), can cause delays because ISPs may throttle emails from IPs with a history of spam or low engagement.

Email marketer from Gmass answers that even if authentication is setup correctly, if emails are sent in large quantities over a new IP without any prior history, these may be marked as spam or delayed, until the new IP earns reputation.

Email marketer from DigitalMarketer mentions that poor sender reputation impacts email delivery as ISPs/mail providers use your reputation as a criteria to determine if your messages will arrive. This can result in inboxing issues such as delays.

Email marketer from Sender.net explains that email delays could arise from a poor sending reputation, even with proper authentication methods enabled, especially when you are on a shared IP address that is also utilized for sending unsolicited or spam emails.

Email marketer from Email Geeks explains that the delay was caused by the PTR record not being configured properly for the static IP pool in SFMC. Switching to a dynamic IP pool resolved the issue.

Expert from Email Geeks explains that the full headers show that SFMC sent the email, but Gmail deferred it, suggesting Gmail deferrals as the issue. He recommends checking SFMC reporting or contacting SFMC support.

Expert from Email Geeks suggests that the issue smells like Gmail deferrals, mentioning that SFMC doesn't track deferrals in a way accessible to clients. Shared IP + Gmail issues in that scenario is kind of a tough way to go.

Expert from Email Geeks shares that SPF not being aligned is not ideal, but acceptable as long as DKIM is aligned.

Expert from Email Geeks explains that the first step is to check the email headers to identify where the delay occurred.

Expert from Spam Resource answers that Email deliverability is dependent on both the reputation of the sending IP address, and the domain used in the ‘From:’ address. If you're on a shared IP that is also used for spam, or one which sends to spam traps, it can take a long time for your emails to be delivered, or even rejected.

Expert from Email Geeks explains the delay could be because SFMC sat on it or Gmail deferred it, and SFMC should be able to provide the deferral reason.

Expert from Word to the Wise explains that even with perfect authentication, the shared IP's overall reputation profoundly impacts deliverability. If other users on the IP engage in practices that harm its reputation, all senders on that IP, including those with proper authentication, may experience delays or filtering.

Documentation from SparkPost Help explains that blacklisting of shared IPs can occur due to the actions of other senders using the same IP. This can lead to significant delivery delays and blockages, regardless of your own authentication efforts.

Documentation from RFC Editor shares that email message transfer agents (MTAs) have different priorities when handling and delivering emails. When a problem arises, they may delay messages until the service is restored or until they are confident they can deliver the email successfully.

Documentation from Salesforce Help explains that when using a shared IP, the reputation is shared among all users of that IP. New Marketing Cloud accounts or those sending a significantly increased volume need to warm up their IP address to establish a positive sending reputation with ISPs.

Documentation from Google Postmaster Tools explains that high spam rates can lead to delivery delays and filtering, even if you have authenticated your emails. Maintaining a low spam rate is crucial for timely delivery to Gmail users.