IIMF helps protect Skype for Business Online users against the most common forms of viruses without degrading the user experience.

In Skype for Business Online, certain files types are blocked by the Intelligent Instant Message Filter (IIMF) application. If your attempts to upload attachments to a conference or to send files to a contact generate an error message, this means either that the contact that you're sending the attachment to doesn't have permission to receive files or that the file type is blocked. Generally, if the menu option to send a file isn't available, this means that the administrator has disabled file transfer capabilities for that user. For more information about Skype for Business Online network requirements, go to the following Microsoft Knowledge Base article:Дў409256 You can't connect to Skype for Business Online, or certain features don't work, because an on-premises firewall blocks the connection More Information If a user doesn't see the option to transfer files, verify that file transfer capabilities are enabled for that user.ДЇirewalled networks must meet the network requirements for Skype for Business Online. For Skype for Business Online administrators If you receive an error message when you send or receive files, make sure that the file type being transferred isn't one of those that is listed in the 'More Information' section. Solution For Skype for Business Online users You can't send pictures directly in an Instant Messaging (IM) conversation.When you send files to contacts, you receive an error message.You can't upload file attachments in Skype for Business Online meetings.In this situation, you may experience the following issues: Assume that in an Office 365 environment, you try to send or receive files or attachments in Lync through Skype for Business Online (formerly Lync Online).

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