It seems that EmailDelivery is still utilizing the SES v1 sending API, as there is no option to add custom headers like in the SMTP Relay settings. When using the Amazon SES API, critical headers such as "List-Unsubscribe-Post: List-Unsubscribe=One-Click" and "List-Unsubscribe" are missing, which poses significant issues.

As AWS announced in the following link, could you please switch to the AWS SES v2 sending API to enable support for custom headers? AWS SES Announcement: https://aws.amazon.com/about-aws/whats-new/2024/03/amazon-ses-headers-sending-email/

Currently, I am faced with a choice: either continue using the SES v1 API provided by EmailDelivery without the required custom headers (which are mandatory for Google and other providers) or switch to the SMTP Relay and forgo the valuable SNS feedback that helps manage complaints and bounces automatically.

In the SMTP Relay settings, I can add custom headers like X-SES-CONFIGURATION-SET: xxx to direct AWS SES to use a specific IP pool rather than the default one. It would be highly beneficial to have this Additional Headers functionality available in the Amazon SES API once EmailDelivery adopts the v2 API.