On September 30, there will be a change in how older browsers and
devices trust Let's Encrypt certificates, resulting in a minor decrease
in compatibility. If you run a typical website, you won't notice a
difference. Devices and browsers running up-to-date software will
continue working fine, and we've taken steps to make sure the vast
majority of older devices will too. If you run a large website, or need
to support less common software (particularly non-browser software),
you'll want to read about the details at:

https://letsencrypt.org/docs/dst-root-ca-x3-expiration-september-2021/

In either case, no action is required from you. We're letting you know
so you can provide answers to any questions your site visitors may have.

Here is a sample hostname from one of your current Let's Encrypt
certificates:

Since 2015 we've served the world with 1.6 billion free certificates,
each one providing security and privacy to people on the Web. It's work
that's 100% funded by charitable donations since we are a nonprofit. If
your company is interested in sponsorship, please email
sponsor@letsencrypt.org. If you can make a donation, we ask that you
consider supporting our work today: https://letsencrypt.org/donate/
Thank you.

• The Let's Encrypt team