Untrusted IMAP certificate in email

my email gives a message that the IMAP certificate is not trusted


[Re-Titled by Moderator]

Original Title: IMAP

iMac 21.5″, macOS 10.15

Posted on Nov 1, 2025 10:36 AM

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Question marked as Top-ranking reply

Posted on Nov 1, 2025 1:47 PM

Check & Correct Account Settings (Client-Side)


This is the most common fix if you are using a custom domain email.

  • Verify IMAP Server Name: Check your email provider's documentation for the exact IMAP server hostname to use. The certificate is tied to a specific name, and any variation will cause this error.
  • Verify Ports and Security: Ensure you are using the correct port (usually 993 for IMAPS) and have SSL/TLS (or sometimes just SSL) enabled for incoming mail.


2. Temporarily Accept/Trust the Certificate

Your email client may allow you to manually trust the certificate.

  • When the error pops up, look for options like "Show Certificate," "Details," or "Trust."
  • In the certificate details window, you can often check a box that says "Always trust this certificate" or "Install Certificate." This tells your device to accept the certificate despite the initial warning.
    • Caution: Only do this if you are absolutely sure the certificate belongs to your legitimate email provider.


3. Remove and Re-add the Email Account

If trusting the certificate doesn't work, or the setting is "stuck," removing and re-adding the account often forces your email client to retrieve the correct, current certificate and settings.

  • Delete the problematic IMAP account from your device or email client.
  • Restart the email client or device (optional, but recommended).
  • Add the email account again, ensuring all settings (server name, port, and security) are accurate.


4. Check Local Security Software

If the certificate is issued by a name that looks like your antivirus software (e.g., "Bitdefender CA"), that program is likely intercepting your secure connection.

  • Temporarily disable any email scanning or SSL/TLS filtering feature in your antivirus or security suite.
  • If that fixes the issue, you'll need to configure your security software to exempt your email client or server from scanning.


5. Contact Your Email Provider

If none of the steps above work, the issue is likely server-side (e.g., an expired or misconfigured certificate on their end).

  • Contact your email host/provider and inform them you are receiving an "untrusted IMAP certificate" error for the server you are using. They will need to verify and fix the SSL certificate on the mail server.

Would you like me to look up the default IMAP settings (server name, port, and security) for a specific email provider you are using?

2 replies
Question marked as Top-ranking reply

Nov 1, 2025 1:47 PM in response to hatch man

Check & Correct Account Settings (Client-Side)


This is the most common fix if you are using a custom domain email.

  • Verify IMAP Server Name: Check your email provider's documentation for the exact IMAP server hostname to use. The certificate is tied to a specific name, and any variation will cause this error.
  • Verify Ports and Security: Ensure you are using the correct port (usually 993 for IMAPS) and have SSL/TLS (or sometimes just SSL) enabled for incoming mail.


2. Temporarily Accept/Trust the Certificate

Your email client may allow you to manually trust the certificate.

  • When the error pops up, look for options like "Show Certificate," "Details," or "Trust."
  • In the certificate details window, you can often check a box that says "Always trust this certificate" or "Install Certificate." This tells your device to accept the certificate despite the initial warning.
    • Caution: Only do this if you are absolutely sure the certificate belongs to your legitimate email provider.


3. Remove and Re-add the Email Account

If trusting the certificate doesn't work, or the setting is "stuck," removing and re-adding the account often forces your email client to retrieve the correct, current certificate and settings.

  • Delete the problematic IMAP account from your device or email client.
  • Restart the email client or device (optional, but recommended).
  • Add the email account again, ensuring all settings (server name, port, and security) are accurate.


4. Check Local Security Software

If the certificate is issued by a name that looks like your antivirus software (e.g., "Bitdefender CA"), that program is likely intercepting your secure connection.

  • Temporarily disable any email scanning or SSL/TLS filtering feature in your antivirus or security suite.
  • If that fixes the issue, you'll need to configure your security software to exempt your email client or server from scanning.


5. Contact Your Email Provider

If none of the steps above work, the issue is likely server-side (e.g., an expired or misconfigured certificate on their end).

  • Contact your email host/provider and inform them you are receiving an "untrusted IMAP certificate" error for the server you are using. They will need to verify and fix the SSL certificate on the mail server.

Would you like me to look up the default IMAP settings (server name, port, and security) for a specific email provider you are using?

Nov 1, 2025 2:46 PM in response to hatch man

It’s quite possible that the certificate is too new for macOS 10.15, as some websites are failing checks with Segtigo certificates and newer macOS versions.


Here is how to manually trust a certificate with Apple Mail: Trust a certificate on Mac - Apple Support


More info on trusted certificates: Updating the Certificate Trust Store on m… - Apple Community


Untrusted IMAP certificate in email

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