What are Queued Emails?

Definition

Queued emails are messages waiting to be sent from your email server. This delay happens when emails can’t be delivered immediately, often due to server limitations or a large volume of outgoing messages. Queued emails remain in the server's outbox until they are processed and sent to recipients.

Example

Say you’re running a flash sale on your online store. You send an email to 20,000 subscribers. However, your server can only handle 5,000 emails per hour. In this case, the system will put the remaining 15,000 emails in a queue. Once there’s more available space, that’s when the queued emails will be sent out.

Why Emails Are Queued

Here are some of the most common reasons why emails get queued.

• High volume. Servers limit how many emails can be sent at once. If your campaign exceeds this limit, emails are queued. This prevents server overload and delivery failures.
• Temporary server issues. Technical problems, like slow connections or outages, may cause delays. Putting emails in a queue keeps them from failing outright.
• Email throttling. ISPs may restrict how many emails they accept at once. Throttling controls the flow and protects sender reputation.
• Large attachments. Emails with large files take longer to process. This can delay the delivery of other messages.
• Spam filters. Some queued emails are also delayed while servers are still confirming that they meet spam standards. This adds extra time but protects sender trust.

How to Manage Queued Emails Effectively

You can’t always control when emails get queued. However, you can try the following steps to manage this situation.

1. Monitor your email server regularly. Check for queued emails in your server dashboard. Address bottlenecks quickly to prevent long delays.
2. Optimize email sending limits. Set realistic sending limits based on your server capacity. Divide large campaigns into smaller batches for smoother processing.
3. Identify and resolve technical issues. Look for server problems, such as poor connectivity or outdated software. Fix these to keep the queue flowing smoothly.
4. Reduce email size. Minimize large attachments or complex design elements. Smaller emails process faster, freeing up the queue.
5. Use a trusted email service provider (ESP). Choose an ESP with high capacity and a good reputation. Reliable platforms handle large volumes efficiently and avoid unnecessary queues.
6. Check spam compliance. Verify your emails meet spam regulations, like valid authentication records. This prevents unnecessary delays/rejections.

Related terms

• Throttling
• Hard Bounce
• SMTP Check

Related articles

• How To Improve Email Deliverability
• How to Reduce Bounce Rate
• Email Deliverability: 101 Guide