SfB 2016 client bug: Mute kills MOH

I encountered a quirky little bug while chasing a Music On Hold (MOH) problem this week.

It seems that in all current flavours of the Office 2016-based client I can lay my hands on (MSI & C2R), activating Mute will suppress the transmission of MOH from the client. This probably isn’t going to be something most users will encounter, but will be exacerbated if you’re running a util that automatically engages Mute – like removing your wireless headset might do.

Its easily reproducible: with the call on hold, toggling Mute on and off will do the opposite to the music. While you’re muted the far end will hear silence & is at risk of hanging up thinking they’ve been disconnected.


This issue won’t however be apparent to external callers if you’re using a Sonus SBC and its in-built MOH feature: that continues to play to the PSTN caller regardless.

Affected releases

I’ve confirmed it occurs on these releases of client:

  • C2R Version 1708, 8431.2094 (Monthly Channel)
  • C2R Version 1710, 8713.1000 (Office Insider)
  • MSI Version 16.0.4549.1000

Revision History

14th October 2017: This is the initial post.


– G.

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