FireBase FCM Notifications and Messaging Queues

I’m a first time user of Firebase and loving the Authentication, real-time database and notifications meaning that all interactions are handled client-side within an Ionic app and consumed via Firebase javascript API.

I would like to start sending triggered emails and communications. Both manually triggered by other user interactions, and on regular intervals (daily/weekly summaries). I feel slightly nervous about depending solely on client-side to process these message, especially as this wouldn’t scale nicely at all.

I’m familiar with writing API’s and Services in .Net so I’d love to write something using the Azure message queue with something like Mandrill or Sendgrid. However this feels a bit OTT and I get the feeling there may be a far simpler solution. Perhaps and off-the-shelf solution or something simple Node.Js?

How does everyone else deal with this?