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Outlook: Why am I experiencing email delays?

This article provides you with steps to check what could be causing your email delays.



Email delay can be frustrating. If you’re like most people, you probably expect email to be near-instantaneous, and most of the time it is. But the complexities of modern email systems and anti-spam efforts can sometimes create a delay. While the causes for delay can vary, it usually falls into one of three groups: greylisting, rate limiting, or a temporary issue with your host. This article explains why emails can sometimes be delayed and how to track down the source of the delay. 




Sometimes email is delayed on purpose as a way of filtering out spam based on the behavior of the sending server. This is called greylisting. During this process, the incoming mail server temporarily rejects a message from a specific sender and asks them to try again. If the email is legitimate, the sending mail server resends the message a few minutes later, and the incoming mail server accepts it. The idea behind this practice is that spammers won’t bother to resend bounced messages because they’re sending mail to thousands of email addresses each day, but a legitimate sender usually will.

Outgoing email delay caused by greylisting is beyond your control because the receiving mail server is responsible. These delays are usually no more than 15 minutes, but can be up to 4 hours.

If you’re experiencing unexpected delay and suspect Spam Filtering to be the cause, you can try update your Domain Spam score.

Rate Limit Thresholds

Rate limits are set to restrict the number of incoming and outgoing emails within a specific time window to limit abuse. Any mail that isn’t allowed through is either added to a delivery queue or temporarily rejected. Most hosts have restrictions like this in place to protect their servers from being overwhelmed by accepting and delivering messages. Delays caused by rate limits are usually temporary and resolve on their own. 

Temporary Host Issue

There are a variety of reasons why your email may be delayed, most of which are unintentional and will resolve on their own. For example, a problem at the sending or receiving mail server will cause the email queue to build up and result in delay which will be resolved once the mail server is back online. However, you may check the network status by clicking here.

Find the Root Cause

To pinpoint the source of the delay, it’s essential to analyze the full message header which contains a detailed log of the network path it took to reach its destination, including how long it was at each location, so you can identify where the delay occurred.

It’s important that you retrieve the message header from the email which has arrived at its destination, not from the sent folder where it originated. Transit information is only in the header of the email which has gone through transit and has since arrived, and isn’t in the original message copy.

Follow these steps to analyze your email header:

  1. Open the email which you received late, and retrieve its complete message header by following the steps for your mail application in the article Displaying Email Headers.
  2. Copy the message header in full.
  3. Now we’re going to use an online email header analyzer. Our favorite is MxToolbox, but you can use any of the top results in a Google search. Go to https://mxtoolbox.com and click Analyze Headers in the top menu.
  4. Paste the message header you just copied into the textbox, and then click the Analyze Header button.
  5. The contents of the header will be analyzed and translated into a table that lists how long the message spent at each location. Review the information to identify any irregularities.

Now that you know where the delay is coming from, you can take action.

TIP: For more articles on Outlook please click here. Alternatively should you wish to contact our Support Center please click here.

Updated on March 9, 2023

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