The email address is valid and the "send daily status reports" is indeed checked.  The outbound mail queue is empty.

Interestingly enough, the emails about the recent upgrades were sent (from OutboundAuditTrailSuccess.log):

2016-10-05 00:26:56,267 - [     36380] 127.0.0.1,postmaster@domain.com,postmaster@domain.com,11995,Subject: Xeams has been updated to version 5.3 build 5858
2016-10-06 01:04:38,796 - [     36386] 127.0.0.1,postmaster@domain.com,postmaster@domain.com,12201,Subject: Xeams has been updated to version 5.3 build 5859

(Domain and IP's have been masq'd, obviously.)