Noted on Checkuser-L mailing list. It appears that emails being sent out to subscribers with Hotmail/MSN email addresses are being bounced, and may not be sending out properly. The Checkuser-L list admins have received a bounce notice for 19 users, which reads:
SMTP error from remote mail server after MAIL FROM:<checkuser-l-bounces@lists.wikimedia.org> SIZE=17772: host mx2.hotmail.com [65.54.188.72]: 550 SC-004 (BAY0-MC1-F13) Unfortunately, messages from 208.80.154.4 weren't sent. We recommend that you contact your Internet service provider. The problem is that too many unwanted messages have been sent from the following IP address above. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors.
Affected users have been sent an email informing of this, and asking them to contact their service provider. Nonetheless, want to ensure you are aware of this in case there is something that can be done from the WMF side.
Version: wmf-deployment
Severity: critical
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=59731
https://bugzilla.wikimedia.org/show_bug.cgi?id=46640