If a list of recipients for an announcement mail is specified by multiple <toAddress>s in the <toAddresses>-tag, like this:
then 2 e-mails will be sent, one to email@example.com, and one to firstname.lastname@example.org.
To have all the recipients for the announcement visible in the mail and to enable reply-to-all (what we use for our release-to-production process) it would be necessary to send an e-mail with all the recipients listed in the to-header of the mail (comma-seperatored), i.e. with a header like this:
To: email@example.com, firstname.lastname@example.org