2011 Outlook for Mac with Yosemite (10.10) and all latest updates, i am having trouble sending emails from Groups in the BCC and even when there are large amounts of emails in the BCC (not as a group) i am also having issues.

Some with up to 50 emails in BCC were sent but most aren't going through.

gives error code 'A message could not be sent' ' The message could not be sent because it has unresolved problems'

with the older versions before i updated to yosemite and outlook for mac updates i could send almost 1000 emails from several groups..