User to see IM sent to them when off-line
When a person sends an IM to a contact who is offline, the message is not sent anywhere. When the off-line contact becomes available they don't know a message was sent to them. Regular Skype and other IM programs show messages received while off-line. My users are hesitant to consider Skype for Business because it's missing this feature.
Jason Gibson commented
even ICQ had that feature back in the 90s!
Totally agree. This is essential feature !