通过Sendgrid, Mailchimp, SES来“取消订阅”邮件类别/类型。

I've got a Rails 3.2 app that will need to send various transactional & bulk (marketing) types of emails. Ideally I'd be able to use a service (like Sendgrid or Amazon SES) to improve deliverability and for unsubscribe support. I've mostly used Sendgrid in the past, but I need the 'unsubscribe' to be just for a specific category of the email (there are around 6 categories). I can't have someone unsubscribing from a marketing email and miss out on notification or invitation emails. Does anyone know of an service that supports this, or does this just have to be done internally? It seems like there's a lot to deal with related to best practices for deliverability, list-unsubscribe, etc. if you manage it yourself. I've got a Rails 3.2 app that will need to send