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Transaction logs grow rapidly on Exchange if the Outlook "Warn me about suspicious names in e-mail addresses" policy is enabled

If you view the transaction logs on your Exchange server, you may find that the log files grow rapidly when a user is logged into multiple Outlook sessions.
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This problem occurs if you have the group policy enabled for the Warn me about suspicious domain names in e-mail addresses setting in Outlook and a user accesses their mailbox from multiple Outlook clients configured in Online mode.

When this policy is enabled, you will find the following data in the Windows Registry.

Key: HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\x.0\outlook\options\mail
DWORD: OutlookEnableSpoofyEmails
Value: 1

Note, x.0 in the above registry path represents the version of Outlook you are using (15.0 = Outlook 2013, 14.0 = Outlook 2010, and 12.0 = Outlook 2007).
To resolve this problem, change the Hide warnings about suspicious domain names in e-mail addresses group policy setting to Not Configured. The following figure shows the path to the policy setting in the group policy editor.

The screen shot for this step

If you need to keep this policy setting enabled, you have two other possible resolutions.
  1. Use only Cached mode profiles to access your Exchange mailbox.
  2. If you are using Online mode profiles, access your Exchange mailbox using only one client at a time.
More information
By default, the Warn me about suspicious domain names in e-mail addresses option is enabled in the Junk E-mail Options dialog box in Outlook. The default configuration is shown in the following figure.

The screen shot for this step

This setting is used to provide a warning if the domain name in an e-mail address for a message you receive is considered suspicious by the Junk E-mail filter in Outlook.

If you enable the  Hide warnings about suspicious domain names in e-mail addresses group policy setting, the Warn me about suspicious domain names in e-mail addresses option is disabled in the Junk E-mail Options dialog box.


Article ID: 2714712 - Last Review: 09/03/2013 09:45:00 - Revision: 5.0

Microsoft Office Outlook 2007, Microsoft Outlook 2010, Microsoft Exchange Server 2010 Enterprise, Microsoft Exchange Server 2007 Enterprise Edition

  • KB2714712