LambdaMailer

Description

LambdaMailer is a simple Serverless mailing system for AWS SES build on µServerless and Scala and deployed using the serverless framework.

The project defines three lambda functions (mailer, bounce, and forwarder) and a dynamodb table to keep track of bounces and complaints.

Lambda Mailer

This lambda function is triggered via SNS, and the payload of the message is a JSON object with the following format:

{
    "to": ["[email protected]"],
    "from": "[email protected]",
    "subject": "test01",
    "body": "<h1>Test Body</h1>",
    "replyTo": "[email protected]",
    "raw": false,
    "attachments": ["s3/path/in/the/attachments/bucket.png"]
}

Field	type	description
to	List[String]	A list of valid email addresses
from	String	Email address that will be use to send the email, this must be an approved email or domain.
subject	String	The subject of the email
body	String	HTML or Plain Text body of the email
replyTo	String	The reply-to email address, can be different from the from email
raw	Boolean	Specifies weather the body of the email is a raw email message (true) or text/html (false)
attachments	List[String]	A list containing keys in the attachments bucket

The mailer will check each email address against the bounce dynamodb table to prevent sending emails to addresses that have been added to this list.

Lambda Mailer Bounce

This lambda function is triggered via SNS. The SNS message is sent by a SES complaint or bounce notification.

Bounces and Complaints are recorded on a dynamodb table. Bounces remain on the table for up to 7 days, complaints remain in the table permanently. The mailer checks every email address against the dynamodb table before sending emails. If the email is found in the table, it is filtered out. You must subscribe the bounce and complaint notifications to the bounce. See the installation section for more information.

Lambda Mailer Forwarder

The forwarder allows you to receive messages sent by a SES rule set.

The forwarder will receive emails sent to the given address and forward them to the associated email addresses.

The association is recorded in a DynamoDB table with a partition key forwardingEmail and a sort key destiantionEmail to uniquely identify the mapping. The dymanodb table is created in the resources section, and the name is available through the environment variable MAPPING_TABLE

In addition, you will need to set the forwarding email addresses in an active SES Rule Set. For more information see the installation instructions below.

Installation

You must build the project before it is deployed using SBT:

sbt assembly

Use the serverless framework to install this project:

serverless deploy --stage dev

Enable bounce and complaint blocking

The lambda mailer defines a lambda function that adds bounce and complaint email addresses to a dynamodb table.

To enable bounce and complaint blocking go SES > Domains > Notifications > Edit Configuration

Under edit configuration select the <STAGE>-mailer-bounce SNS Topic for both Bounces and Complaints.

Save Config, and you are done!

Enable email forwarding

For the forwarder to work properly, you will need to create/edit the SES Rule Set after the application has been launched:

1. Go to SES -> Rule Set -> Vie Active Rule Set
2. Create or edit an existing Rule Set
3. Add one or more verified recipients, these are email addresses to reach your forwarder, e.g. [email protected]
4. Add an action S3. Find or select the lambda-mailer-dev-forwarders3bucket-XXXXXXXXXX bucket. To find the exact name of the S3 bucket:
   1. go to CloudFormation and select the lambda-mailer-<STAGE> stack
   2. select the Outputs section and copy the value of the ForwarderS3BucketName which should look like lambda-mailer-dev-forwarders3bucket-XXXXXXXXXX
5. Add a Lambda action and select the lambda-mailer-<STAGE>-forwarder
6. Click on Save Rule
7. In the Missing Permission pop-up click Add permissions

Uninstall

serverless remove