But here is an interesting article that was I was pointed to by some folks at Microsoft here in Canada.
My team and I have been doing alot of work with Office 365 Wave 15. Migrations, co-existence, hybrid with Lync on-premises. And was advised that Lync Online is going to be changing their certificates as of June 1st 2013.
I wont post about the changes, as they can be found here,
Long story short from the article, you will need to download the Baltimore Root certificate if you do not use Windows Update on a regular biases, or you have security policies in place that do not allow for all trusted root certificate authority certificates to be stored on your servers.
You can download the root certificate here.
NOTE: This root certificate will need to be installed on every server that will come in contact with Lync Online.
Steps to install
Step 1: Download and Save the crt file above.
Step 2: Install Certificate into Trusted Root Certificate Store
Open, MMC (Start -> Run, type mmc)
Add the Certificates Snap in
Select Local Computer, then click Finish
Once the Certificates Snap-in is loaded, expand Certificates (Local Computer), Trusted Root Certification Authorities then Certificates. Right click Certificates, All Tasks and Import.
Click Next, Browse to the file that you downloaded above.
Click Next and Finish, you should receive a message that the import was successful.
To confirm check the list of root certificates to see if Baltimore CyberTrust Root is installed.
And there we have it. If you do not download specific updates, or have company regulations against storing specific certificates, this certificate needs to be installed by June 1st 2013 or any federation/hybrid/co-existence you have with Lync Online will stop working.
Thank you for reading, I hope I can start writing my co-existence articles very soon.