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Troubleshooting 'Invalid Mail Server Certificate' Warnings

This Article Applies to:

  • Avast Small Business Solutions
  • Avast Small Office Protection


Mail Shield in Avast Antivirus uses an advanced scanning method for incoming and outgoing emails over SSL/TLS secured connections. Third-party email clients have their own certificate stores and may require extra configuration to avoid warnings about invalid mail server certificates when sending or receiving emails. If you are receiving such warnings, importing the Avast's Mail Shield certificate into your email client should help resolve the issue.

Each individual account in your email client needs to be configured as required by your email provider. Refer to your email client's and provider's documentation for instructions.


To export your the Mail Shield certificate:

  1. Open the Antivirus client
  2. Go to Menu, then select Settings
  3. Click Search in the top right corner
  4. Type geek:area and hit ENTER
  1. In the Mail Shield section, ensure the checkbox next to Scan SSL connections is ticked, then click Perform next to Export certificate

  1. Select the export location
  2. In the Avast export confirmation dialog, click OK

Once you have exported the certificate, import it to your email client.

The certificate-related options are usually part of an email client's Privacy & Security settings (or Trust Center settings in Outlook in particular). If you are unsure how to import your certificate, please refer to your email client's and provider's documentation for more detailed instructions.

Importing Avast's Mail Shield certificate to your email client should stop warnings about an invalid mail server certificate. If you keep encountering the same issue after the import, contact our Business Support team for further assistance.