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Too many simultaneous connections

  1. Mailbird
  2. Troubleshooting
  3. Issues Sending or Receiving Emails
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Oliver Jackson
  • June 18, 2025 16:18
  • Updated

🚫 Why You’re Seeing a 'Too Many Simultaneous Connections' Error

If your email account isn't syncing properly, or you're seeing an error that says "Too many simultaneous connections", this article explains why it happens, and how to fix it.

📡 Understanding IMAP Connection Limits

All IMAP servers place a limit on the number of active connections they can handle at one time. Naturally, these limit are beyond our control, so when too many applications (such as Gmail, Mailbird, and mobile mail apps) try to connect to your email server simultaneously, some of them will be denied access, resulting in sync errors or emails not going/coming through.

For example, Gmail allows up to 15 connections on its IMAP servers. By default, Mailbird uses 5 simultaneous connections, so if you're also using a browser, phone, or another email client, it's easy to exceed that 15-connection limit. Another example is Yahoo, which appears to allow as few as 5 simultaneous connections.

🔧 How to Reduce Mailbird’s number of used connections

To avoid reaching your email server's connection limit, Mailbird offers a solution which can help improve performance across all of your devices. This involves reducing the number of connections used by Mailbird itself. Here's how:

  1. Open the Mailbird Menu (three horizontal lines in the top-left corner).

  2. Click on Settings.

  3. Go to the Accounts tab.

  4. Select the email account which is experiencing problems, and click Edit.

  5. At the bottom of the settings window, locate the Connections slider and reduce it to 2.

  6. If you're still experiencing issues, try setting it to 1 and check again.

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Although having more connections is generally better, reducing them can significantly improve stability if you're encountering delays or connection errors in Mailbird.

📱 Don’t Forget Your Other Devices

Reducing Mailbird’s connections may not be enough if your other devices or email clients are also consuming too many connections. We recommend checking and adjusting the connection settings on:

  • Your mobile mail apps

  • Any web-based email clients (e.g., Gmail in a browser)

  • Other desktop email programs (e.g. Outlook)

💬 Need More Help?

We hope this article resolved your issue! If you still need assistance, feel free to contact our Customer Happiness Team. We’re always here to help.

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