Avast Antivirus: Troubleshooting warnings about invalid mail server certificates when sending and receiving e-mails

Summary

After installing Avast Antivirus, some 3rd party mail clients such as Mozilla Thunderbird, SeaMonkey, or The Bat! may show a warning message that the mail server certificate is invalid when you send and receive e-mails.

The Mail Shield in Avast Antivirus uses an advanced scanning method for incoming and outgoing e-mails over SSL/TLS secured connections, which works transparently for most mail clients and normally doesn't need additional configuration. Mozilla Thunderbird, Sea Monkey, and the Bat! have their own certificate stores and require extra configuration to avoid warnings about invalid mail server certificates.

To stop warnings about invalid mail server certificates, export the Mail Shield certificate and import it to your mail client's certificate store using the directions in this article.

To export the Mail Shield certificate:

  1. Open the Avast user interface and click Settings.
  2. In the Settings window, select Components and click Customize next to Mail Shield.
  3. In the Mail Shield Settings window, select SSL scanning from the left panel and ensure the box next to Scan SSL connections is ticked. Then, click Export certificate.
  4. Select a location to save the exported Mail Shield certificate (for example, your Windows Desktop) and click Save.
  5. When a message appears that "Avast Mail Shield has been successfully exported" click OK.
  6. Import the Mail Shield certificate into your mail client. Select your mail client below to view specific instructions:
Each e-mail account in your mail client needs to be configured as required by your mail provider. Refer to your mail client's and mail provider's documentation for instructions.

Importing the Mail Shield certificate to Mozilla Thunderbird

To import the Mail Shield certificate to the Mozilla Thunderbird certificate store:

  1. In Mozilla Thunderbird click the menu icon (three horizontal lines) at the top right corner to open the Application menu and select Options....
  2. Select Advanced on the top right, click the Certificates tab, and then click View Certificates to open the Certificate Manager.
  3. In Certificate Manager select the Authorities tab, click Import..., ...and locate the Mail Shield certificate you exported from Avast 2015. Select the file and click Open.
  4. Confirm that you want to Trust this CA to identify websites and click OK.
  5. When the Certificate Manager screen appears again, select the Servers tab, ...and ensure that there is no entry entitled "Avast Mail Scanner". If this entry exists, delete all certificates connected to Avast Mail Scanner on the Servers tab. Then click OK to close the Certificate Manager, ...and click OK in the Options window to apply changes.

Importing the Mail Shield certificate to SeaMonkey

To import the Mail Shield certificate to the SeaMonkey certificate store:

  1. In SeaMonkey click the Edit menu on the top and select Preferences....
  2. In Preferences expand the Privacy & Security group on the left, select the Certificates section, and click Manage Certificates....
  3. In the Certificate Manager select the Authorities tab, click Import..., ...and locate the Mail Shield certificate you exported from Avast 2015. Select the file and click Open.
  4. Confirm that you want to Trust this CA to identify websites and click OK.
  5. When the Certificate Manager appears again, select the Servers tab, ...and ensure that there is no entry entitled "Avast Mail Scanner". If this entry exists, delete all certificates connected to Avast Mail Scanner on the Servers tab. Then click OK to close the Certificate Manager, ...and click OK in the Preferences window to apply changes.

Importing the Mail Shield certificate to The Bat!

To import the Mail Shield certificate to The Bat! certificate store:

  1. Open The Bat!, click the Tools menu on the top, and select Address Book.
  2. In Address Book, click View and select Certificate Address Books.
  3. Right-click the Trusted Root CA group on the left side of the Address Book and select New Contact from the context menu.
  4. In the General tab enter "Avast Mail Scanner Root" in the First name field.
  5. Select the Certificates tab, click Import..., ...and locate the Mail Shield certificate you exported from Avast 2015. Select the file and click Open.
  6. Once the Mail Shield certificate is imported click OK for to apply changes and exit the Address Book.
  • Avast 12.x
  • Avast Internet Security 12.x
  • Avast Pro Antivirus 12.x
  • Avast Free Antivirus 12.x
  • Microsoft Windows 10 Home / Pro / Enterprise / Education
  • Microsoft Windows 8.1 / Pro / Enterprise
  • Microsoft Windows 8 / Pro / Enterprise
  • Microsoft Windows 7 Home Basic / Home Premium / Professional / Enterprise / Ultimate
  • Microsoft Windows Vista Home Basic / Home Premium / Business / Enterprise / Ultimate
  • Microsoft Windows XP Home / Professional / Media Center Edition

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