And all you need to do is ignore the exception on the bad recipients and continue processing...
javax.mail.internet.AddressException: Illegal whitespace in address in string ``i5 R&D Build''
at javax.mail.internet.InternetAddress.checkAddress(InternetAddress.java(Compiled Code))
at javax.mail.internet.InternetAddress.parse(InternetAddress.java(Compiled Code))
at javax.mail.internet.InternetAddress.parseHeader(InternetAddress.java:547)
at javax.mail.internet.MimeMessage.getAddressHeader(MimeMessage.java:657)
at javax.mail.internet.MimeMessage.getRecipients(MimeMessage.java:482)
at javax.mail.Message.getAllRecipients(Message.java:268)
at javax.mail.internet.MimeMessage.getAllRecipients(MimeMessage.java:497)
at com.atlassian.confluence.mail.Mail.getRecipients(Mail.java:356)
at com.atlassian.confluence.mail.Mail.getRecipientsForSearch(Mail.java:332)
I've updated Confluence so that it now reads the invalid email address as plain text without parsing. This will allow indexing to proceed.