"After doing
more research and tests I have confirmed that both Lync Server 2010 and Lync
Server 2013 issue self-signed certificate with SHA-1 algorithm to Lync clients
in the meantime both Skype for Business Server 2015 and Skype for Business
online issue self-signed certificate with SHA-2 algorithm to their clients.
After doing plenty of
research we cannot change Hash algorithm of the self-signed certificate issued
by Lync Server 2010 and Lync Server 2013 so we’d like to suggest you perform
the upgrade to Skype for Business Server 2015 before January 1, 2017. "
After doing some google search I found this one from November 2014,SHA-1 client issue as it say that clients does not have to do anything but this is an technical issue.
And since also Lync 2010 is out of mainstream support well now it's the time to plan for your upgrade.

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