Symfony version(s) affected: 5.2.4
symfony/amazon-mailer still uses AWS Signature Version 3 (signature starting with AWS3-HTTPS) while it is not supported anymore.
As mentioned in the aws documentation (https://docs.aws.amazon.com/ses/latest/DeveloperGuide/using-ses-api-authentication.html) :
Beginning October 1st, 2020, Amazon SES will only support requests signed using Signature Version 4. If you use an older version of the AWS Signature, you must adopt AWS Signature Version 4 prior to that date.