When Using Chrome (and apparently Firefox) get below error message when trying to access Exchange 2016 OWA & ECP (Exchange Admin Centre).
Your connection is not secure
The website tried to negotiate an inadequate level of security.
XXXXXXXXXX.domain uses security technology that is outdated and vulnerable to attack. An attacker could easily reveal information which you thought to be safe. The website administrator will need to fix the server first before you can visit the site.
Error code: NS_ERROR_NET_INADEQUATE_SECURITY
or
This site can’t be reached
The webpage at https://mail.yoursite.com/owa might be temporarily down or it may have moved permanently to a new web address.
ERR_SPDY_INADEQUATE_TRANSPORT_SECURITY
Internet explorer (IE) and Windows Edge work as expected
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FIX
Fixed using IIS Crypto tool https://www.nartac.com/Products/IISCrypto
Selected Best practices button and Apply
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As per post on https://support.mozilla.org/en-US/questions/1143320