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Real-Time Scanning can cause slow response times in Thunderbird


Affected Suites:
McAfee 2013 suites

Affected Products:

Affected Applications:
Mozilla Thunderbird


When you attempt to send large emails or emails with large attachments (30 MB or larger) through Thunderbird, you may notice a slowdown lasting between 10 seconds and 2 minutes. 

In some cases, Thunderbird may temporarily display a Not Responding message.


This delay is caused by Real-Time Scanning as it scans the attachment to ensure that you are not unintentionally sending an infected email.


McAfee is investigating ways to improve scanning performance for large attachments in the next product release.

Sending smaller emails or emails with smaller attachments does not cause any noticeable delay.  This is because the email or attachment takes less time to scan.

NOTE: Delays of this type are more noticeable on older computers, especially those with single core processors and limited amounts of RAM. Additionally, many ISPs prohibit sending large emails or attachments of the size that would cause this sort of delay.


Disable Email Attachment Scan

  1. Double-click the M icon in your taskbar.
  2. Open the Virus and Spyware Protection drawer.
  3. Select Real-Time Scanning.
  4. Open the Settings drawer.
  5. Remove the check from the box beside Scan these attachments and locations: Email attachments.

    IMPORTANT: By disabling this feature you will prevent the Real-Time Scanner from scanning attachments you send. If you choose this option, McAfee recommends that you right-click and scan the file manually before you attach and send it.