The easiest option for monitoring Amazon RDS (and any other AWS, for that matter) is Amazon CloudWatch , which provides a reliable, scalable and flexible monitoring solution that you can start using within minutes and in particular includes Alarms :
[...] Alarms can automatically initiate actions on your behalf based on the specified parameters. An alarm monitors one metric over a specified time period, and performs one or more actions based on the value of the metric relative to a given threshold for a number of time periods. An action is a notification sent to an Amazon SNS topic or auto-scaling. [...] [emphasis mine]
Amazon SNS supports notifications via several transport protocols, in turn, among these Email and Email-JSON, see the corresponding FAQ. What are the different delivery formats / transports for receiving notifications? :
[...] Customers can choose one of the following transports as part of subscription requests:
- [...]
- "Email", "Email-JSON" - messages are sent to registered addresses in the form of email. Email-JSON sends notifications as a JSON object, and email sends text email.
This metric is the FreeStorageSpace RDS metric (see Amazon RDS Dimensions and Metrics for more information on the available), as described in Scaling Database Instance Storage :
Attention!
We strongly recommend that you constantly monitor the FreeStorageSpace RDS metric published on CloudWatch to ensure that your database instance has enough free space for storage. For more information on monitoring RDS DB instances, see Viewing DB Instance Metrics .
Accordingly, you need to create a mirror image of the alarm or approach the threshold reported to you by AWS in the console, publish it in the SNS topic and subscribe to this question via the email address of your choice.