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. However, if you suspect your incoming email delay is the result of greylisting, check to see if you have Spam Hammer enabled. Spam Hammer employs greylisting in the fight against spam, and it's methods are known to cause delay in some cases. 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 Hammer to be the cause, you can disable Spam Hammer on either your domain or email addresses individually, or turn it off it all together. See Spam Hammer for more information.
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. However, some mail hosts employ rate limiting on all inbound email from other hosts as a way of encouraging users to use their services. If you suspect this is what's happening, contact the mail host for more information.
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, problems like these are usually temporary so there's nothing to worry about.
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:
- 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.
- Copy the message header in full.
- 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.
- Paste the message header you just copied into the textbox, and then click the Analyze Header button.
- 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.Are your messages being delayed at a Bluehost server? Are your incoming messages being delayed?
If you're experiencing unexpected delay on your incoming messages, check to see if Spam Hammer is enabled for your domain or email address. Spam Hammer uses greylisting to filter out spam which can delay emails. See Spam Hammer for more information.Are your outgoing messages being delayed?
This could be symptomatic of a temporary issue at Bluehost. If this continues for more than 24 hours, contact Technical Support with the full headers of the message ready.Are your messages being delayed at a non-Bluehost server? Are your incoming messages being delayed?
- If you're using POP3 settings on your mail client, see if you can increase the POP3 fetch frequency. If that isn't possible, you may want to use IMAP or use another mail client that does allow you to change those settings, instead.
- If you're forwarding mail to another host and that host is delaying messages, contact them for more information or consider creating an email account for that address as an alternative to using a forwarder.
- Are the delayed emails part of a marketing campaign being sent to a list of subscribers? If so, check out Getting Started with Email Marketing for information on maximizing the deliverability of your marketing messages.
- If you're sending the emails to individuals and only a few of them are delayed, the receiving host may have greylisted your messages. You can wait to see if the issue resolves itself, or contact the mail host and ask about the problem.
- If the delay is occurring to more than a few destinations, make sure that your domain has an SPF record that allows Bluehost to send messages on behalf of your domain.