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terraform-mail-forwarder

Forward incoming mail using SES+Lambda

Introduction

This module provisions a NodeJS script as a AWS Lambda function that uses the inbound/outbound capabilities of AWS Simple Email Service (SES) to run a "serverless" email forwarding service.

Use this module instead of setting up an email server on a dedicated EC2 instance to handle email redirects. It uses AWS SES to receive email and then trigger a Lambda function to process it and forward it on to the chosen destination. This script will allow forwarding emails from any sender to verified destination emails (e.g. opt-in).

Limitations

The SES service only allows sending email from verified addresses or domains. As such, it's mostly suitable for transactional emails (e.g. alerts or notifications). The incoming messages are modified to allow forwarding through SES and reflect the original sender. This script adds a Reply-To header with the original sender's email address, but the From header is changed to display the SES email address.

For example, an email sent by John Doe <jonh@example.com> to hello@example.com will be transformed to:

From: John Doe at john@example.com <hello@example.com>
Reply-To: john@example.com

To override this behavior, set a verified fromEmail address (e.g., noreply@example.com) in the config object and the header will look like this.

From: John Doe <noreply@example.com>
Reply-To: john@example.com

NOTE: SES only allows receiving email sent to addresses within verified domains. For more information, see: http://docs.aws.amazon.com/ses/latest/DeveloperGuide/verify-domains.html


Initially SES users are in a sandbox environment that has a number of limitations. See:
http://docs.aws.amazon.com/ses/latest/DeveloperGuide/limits.html

## Usage


For a complete example, see [examples/complete](examples/complete).

For automated tests of the complete example using [bats](https://github.com/bats-core/bats-core) and [Terratest](https://github.com/gruntwork-io/terratest) (which tests and deploys the example on AWS), see [test](test).

```hcl
variable "relay_email" {
  default     = "example@example.com"
  description = "Email that used to relay from"
}

variable "forward_emails" {
  type = map(list(string))

  default = {
    "some_email@example.com"  = ["my_email@example.com"]
    "other_email@example.com" = ["my_email@example.com"]
  }

  description = "Emails forward map"
}

module "ses_lambda_forwarder" {
  source = "cloudposse/ses-lambda-forwarder/aws"
  # Cloud Posse recommends pinning every module to a specific version
  # version = "x.x.x"

  namespace  = var.namespace
  stage      = var.stage
  name       = var.name
  delimiter  = var.delimiter
  attributes = var.attributes
  tags       = var.tags

  region = var.region
  domain = var.domain

  relay_email    = var.relay_email
  forward_emails = var.forward_emails
}

Makefile Targets

Available targets:

  help                                Help screen
  help/all                            Display help for all targets
  help/short                          This help short screen
  lint                                Lint terraform code

Requirements

Name Version
terraform >= 0.13.0
aws >= 2.0
external >= 1.2
local >= 1.3
template >= 2.0

Providers

Name Version
aws >= 2.0

Modules

Name Source Version
artifact cloudposse/module-artifact/external 0.7.0
this cloudposse/label/null 0.25.0

Resources

Name Type
aws_iam_policy.lambda resource
aws_iam_role.lambda resource
aws_iam_role_policy_attachment.lambda resource
aws_lambda_alias.default resource
aws_lambda_function.default resource
aws_lambda_permission.ses resource
aws_route53_record.default resource
aws_route53_record.mx resource
aws_route53_record.txt resource
aws_s3_bucket.default resource
aws_s3_bucket_policy.default resource
aws_ses_active_receipt_rule_set.default resource
aws_ses_domain_identity.default resource
aws_ses_domain_identity_verification.default resource
aws_ses_receipt_rule.default resource
aws_ses_receipt_rule_set.default resource
aws_caller_identity.current data source
aws_iam_policy_document.assume data source
aws_iam_policy_document.lambda data source
aws_iam_policy_document.s3 data source
aws_route53_zone.default data source

Inputs

Name Description Type Default Required
access_log_bucket_name Name of the S3 bucket where s3 access log will be sent to string "" no
additional_tag_map Additional key-value pairs to add to each map in tags_as_list_of_maps. Not added to tags or id.
This is for some rare cases where resources want additional configuration of tags
and therefore take a list of maps with tag key, value, and additional configuration.		 map(string) {} no
artifact_filename Artifact filename string "lambda.zip" no
artifact_url URL template for the remote artifact string "https://artifacts.cloudposse.com/$${module_name}/$${git_ref}/$${filename}" no
attributes ID element. Additional attributes (e.g. workers or cluster) to add to id,
in the order they appear in the list. New attributes are appended to the
end of the list. The elements of the list are joined by the delimiter
and treated as a single ID element.		 list(string) [] no
context Single object for setting entire context at once.
See description of individual variables for details.
Leave string and numeric variables as null to use default value.
Individual variable settings (non-null) override settings in context object,
except for attributes, tags, and additional_tag_map, which are merged.		 any 
{
  "additional_tag_map": {},
  "attributes": [],
  "delimiter": null,
  "descriptor_formats": {},
  "enabled": true,
  "environment": null,
  "id_length_limit": null,
  "label_key_case": null,
  "label_order": [],
  "label_value_case": null,
  "labels_as_tags": [
    "unset"
  ],
  "name": null,
  "namespace": null,
  "regex_replace_chars": null,
  "stage": null,
  "tags": {},
  "tenant": null
}
 no
delimiter Delimiter to be used between ID elements.
Defaults to - (hyphen). Set to "" to use no delimiter at all.		 string null no
descriptor_formats Describe additional descriptors to be output in the descriptors output map.
Map of maps. Keys are names of descriptors. Values are maps of the form
{<br> format = string<br> labels = list(string)<br>}
(Type is any so the map values can later be enhanced to provide additional options.)
format is a Terraform format string to be passed to the format() function.
labels is a list of labels, in order, to pass to format() function.
Label values will be normalized before being passed to format() so they will be
identical to how they appear in id.
Default is {} (descriptors output will be empty).		 any {} no
domain Root domain name string n/a yes
enabled Set to false to prevent the module from creating any resources bool null no
environment ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT' string null no
forward_emails Map of forward emails map(list(string)) 
{
  "ops@example.com": [
    "destination@example.com"
  ]
}
 no
id_length_limit Limit id to this many characters (minimum 6).
Set to 0 for unlimited length.
Set to null for keep the existing setting, which defaults to 0.
Does not affect id_full.		 number null no
label_key_case Controls the letter case of the tags keys (label names) for tags generated by this module.
Does not affect keys of tags passed in via the tags input.
Possible values: lower, title, upper.
Default value: title.		 string null no
label_order The order in which the labels (ID elements) appear in the id.
Defaults to ["namespace", "environment", "stage", "name", "attributes"].
You can omit any of the 6 labels ("tenant" is the 6th), but at least one must be present.		 list(string) null no
label_value_case Controls the letter case of ID elements (labels) as included in id,
set as tag values, and output by this module individually.
Does not affect values of tags passed in via the tags input.
Possible values: lower, title, upper and none (no transformation).
Set this to title and set delimiter to "" to yield Pascal Case IDs.
Default value: lower.		 string null no
labels_as_tags Set of labels (ID elements) to include as tags in the tags output.
Default is to include all labels.
Tags with empty values will not be included in the tags output.
Set to [] to suppress all generated tags.
Notes:
The value of the name tag, if included, will be the id, not the name.
Unlike other null-label inputs, the initial setting of labels_as_tags cannot be
changed in later chained modules. Attempts to change it will be silently ignored.		 set(string) 
[
  "default"
]
 no
lambda_runtime Lambda runtime string "nodejs12.x" no
name ID element. Usually the component or solution name, e.g. 'app' or 'jenkins'.
This is the only ID element not also included as a tag.
The "name" tag is set to the full id string. There is no tag with the value of the name input.		 string null no
namespace ID element. Usually an abbreviation of your organization name, e.g. 'eg' or 'cp', to help ensure generated IDs are globally unique string null no
regex_replace_chars Terraform regular expression (regex) string.
Characters matching the regex will be removed from the ID elements.
If not set, "/[^a-zA-Z0-9-]/" is used to remove all characters other than hyphens, letters and digits.		 string null no
region AWS Region the SES should reside in string n/a yes
relay_email Email that used to relay from string n/a yes
s3_bucket_encryption_enabled When set to 'true' the 'aws_s3_bucket' resource will have AES256 encryption enabled by default bool true no
spf DNS SPF record value string "v=spf1 include:amazonses.com -all" no
stage ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release' string null no
tags Additional tags (e.g. {'BusinessUnit': 'XYZ'}).
Neither the tag keys nor the tag values will be modified by this module.		 map(string) {} no
tenant ID element _(Rarely used, not included by default)_. A customer identifier, indicating who this instance of a resource is for string null no
tracing_config_mode Can be either PassThrough or Active. If PassThrough, Lambda will only trace the request from an upstream service if it contains a tracing header with 'sampled=1'. If Active, Lambda will respect any tracing header it receives from an upstream service. string "PassThrough" no
versioning_enabled A state of versioning. Versioning is a means of keeping multiple variants of an object in the same bucket bool true no

Outputs

Name Description
artifact_base64sha256 Base64 encoded SHA256 hash of the artifact file
artifact_file Full path to the locally downloaded artifact
artifact_git_ref Git commit hash corresponding to the artifact
artifact_url URL corresponding to the artifact
lambda_function_arn Lamnda Function ARN
lambda_function_source_code_size The size in bytes of the Lambda Function .zip file
lambda_function_version Latest published version of the Lambda Function
lambda_iam_policy_arn Lamnda IAM Policy ARN
lambda_iam_policy_id Lamnda IAM Policy ID
lambda_iam_policy_name Lamnda IAM Policy name
s3_bucket_arn Lamnda IAM Policy ARN
s3_bucket_domain_name Lamnda IAM Policy ARN
s3_bucket_id Lamnda IAM Policy name
ses_domain_identity_arn The ARN of the domain identity
ses_domain_identity_verification_arn The ARN of the domain identity
ses_receipt_rule_name The name of the SES receipt rule
ses_receipt_rule_set_name The name of the SES receipt rule set

References

For additional context, refer to some of these links.

  • aws-lambda-ses-forwarder - A Node.js script for AWS Lambda that uses the inbound/outbound capabilities of AWS Simple Email Service (SES) to run a "serverless" email forwarding service.

History

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