However, until Skype starts blocking spam itself, this is the most effective way to protect yourself from uninvited guests.
If you're not sure if the other person's organization has open federation, contact them first by phone or email to ask.
If the organization has open federation, you can add users in that organization to your Skype for Business Contacts list by adding their Skype for Business address to your contacts list.
I’ve been used to receiving spam on IM clients such as MSN Live Messenger and Adium for a long time now.
What usually happens is a contact I haven’t spoken to for years will suddenly pop up telling me to click on this “great link” or implore me to “check out this great site – you won’t believe it! However, increasingly I’ve been experiencing this problem with Skype too and according to the Skype forums, I’m not alone.
Skype for Business is not designed to be used with shared accounts for the purpose of instant messaging and presence.