Can I use Amazon SQS as a delay queue before sending to SNS?

Unfortunately this is not yet available out of the box. The missing part is the generation of Amazon SNS notifications on message arrival/visibility by an Amazon SQS queue, be it via push (similar to Amazon S3 notifications, or via poll similar to Amazon Kinesis subscriptions (see The Pull/Push Event Models for more on the difference), which would both allow to directly connect an AWS Lambda function to the resp. SQS delay queue events, see e.g.:

• Lambda with SQS

That being said, you can work around this limitations in a few ways, for example:

• trigger your Lambda function on schedule (e.g. once per minute), and poll your SQS delay queue from there
  • scheduled Lambda functions are an eagerly awaited missing Lambda feature in turn, but it is more easily worked around, be it either by a cron job of yours, or Eric Hammond's Unreliable Town Clock (UTC) for example

The AWS Lambda team has delivered many/most similar feature requests over recent month' btw., so I would expect them to offer both SQS event handling and scheduled Lambda functions over the course of the year still.

In early 2019, this problem can be solved in a few different ways:

• SQS as an Event Source to Lambda (finally announced 2018-06-28), similar to the OP's original design.

• AWS Step Functions (announced 2016-12-01), using a wait step for the delay.

• DynamoDB Streams with Lambda triggers (announced 2017-02-17), using TTL expiration on items to fire the Lambda trigger.

As SNS has a topic limit of 100,000 per account, I would recommend using Amazon SES to send the emails (62,000 free emails/month could help with implementation cost decisions).