This article explains why a message may be wrongly identified as "possible spam" by the group's spam filter and provides actions that moderators may take to address the issue.

We want to give Yahoo! Groups users the best possible experience by limiting spam, and unfortunately, spam filters sometimes misdiagnose emails as spam. There are many factors that may cause a message to be marked as a spam including:

• The IP address of the sender
• The content of the message
• Specific links in the content

RESOLUTION 1

Group moderators with the privilege to approve messages may approve a message in the spam folder, which will identify to our system that the message was wrongly marked as spam. Over time, doing so will improve the accuracy of the system and reduce "false positives." 

RESOLUTION 2

If many messages in the group are being erroneously marked as possible spam, a group moderator with the privilege to change group settings may turn off the spam filtering for the group.

Unfortunately, at this time, we don't offer the option to customize the spam filter on a per group basis or to "whitelist" certain users to always allow their messages to go through.