ISPs/NSPs with customers running self hosted or on-premises Exchange may want to be aware of this.

https://krebsonsecurity.com/2021/03/at-least-30000-u-s-organizations-newly-hacked-via-holes-in-microsofts-email-software/

https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/