Office 365 and Outlook 2015 (Mac)

Recently a message has been appearing that an encrypted channel could not be created between the Outlook client and Office 365. The message states that the certificate is invalid i.e webdesign***.*** (which we do not have a certificatee for) and could not connect to It allows the option to continue unencrypted. How do I resolve this issue?
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Alan HardistyCo-OwnerCommented:
Do you mean Outlook 2016 for Mac as there is no 2015 for a Mac?

What OS version is on the Mac?

Sounds like it could be a DNS issue with a conflict pointing autodiscover to somewhere other than Microsoft.  Have you checked your domain setup to make sure that ALL the Office 365 DNS settings are as Microsoft need them in the 365 portal?


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