Currently there is a known issue with non-receipt of certain emails sent from the community website.

The issue is affecting those residents using Yahoo mail and their subsidiary providers.
These include:
AT&T / SBCglobal: @att.net, @sbcglobal.net, @bellsouth.net, @pacbell.net, @prodigy.net, @swbell.net, @ameritech.net, @snet.net, @wans.netComcast / Xfinity @comcast.net
Verizon: @verizon.net
Frontier: @frontier.com, @frontiernet.net, @myfrontiermail.com
Cox Communications: @cox.net
AOL: @aol.com, @aim.com, @netscape.net, @cs.com, @wmconnect.com
Other regional or legacy ISPs: @citlink.net, @epix.net, @gte.net, @bellatlantic.net, @newnorth.net

This is a website vendor issue and they are working on it.

Here is their latest update:
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5/22 Update - Deferred Emails
Hello,
As of 5/20, we have rolled out two significant updates to our email system.
These updates are continuing to propagate across the affected providers. Because these providers must process and recognize the changes on their end, improvements may take some time to fully take effect. We are continuing to closely monitor delivery performance as the changes are accepted.
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The Webmasters will continue to monitor the situation and provide updates.