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Full Email Storage / Backup API for AWS S3, Google Cloud Storage, Azure Blob

CloudMailin allows you to receive any volume of email over HTTP via HTTP POST Webhook. For some time it has been possible to offload the sending of email attachments to Cloud Storage such as Amazon Web Services (AWS) S3, Google Cloud Platform Storage or Azure Blob Storage.

It's also possible to send the entire email to CloudStorage, opening up new possibilities for your HTTP server to process inbound emails.

You can send the full email to:

• Amazon Web Services (AWS) S3
• Microsoft Azure Blob Storage
• Google Cloud Platform Cloud Storage

Why send email directly to Cloud Storage?

Sending your full email, rather than just the email attachments to AWS S3, Google Cloud Storage or Azure Blob Storage opens new possibilities for receiving inbound emails via Webhook. You could process the email asynchronously, use the system as a backup or work more effectively with serverless functions for example.

Email storage formats

There are two formats available for full email storage raw and parsed JSON:

Format	Description
RAW	The original, unparsed email with headers and body.
JSON	A fully parsed email in JSON format. This format is the same as the JSON format sent to your Webhook.

Send the full email to AWS S3

Once you have enabled the feature you setup the Full Message storage in a very similar way to setting up attachment storage.

Grant CloudMailin permission send email to your AWS S3 Bucket

There are several ways that you can grant permission for CloudMailin to create files in your S3 Bucket. The simplest is to use the AWS website.

1. Go to the AWS Management Console https://console.aws.amazon.com and Sign in.
2. Click on the S3 Tab, then select your bucket (or create a new one)
3. Click on permissions the button
4. Scroll down to the Access control list (ACL) panel
5. Click Edit and then Add grantee
6. In the grantee field from above, paste the CloudMailin Canonical ID, choose write and then save

AWS Canonical ID: 83fec836f8a832fae9c46e100739b635be3b3636d14887e1c7616e2dba1a88c0

You should now have granted CloudMailin permission to add files to your S3 bucket. You can now Setup CloudMailin to receive the emails in its Webhook.

Send the full email to Azure Blob Storage

It's possible to configure CloudMailin to send the full email directly to an Azure Blob Storage container. CloudMailin writes to the container using a Shared Access Signature (SAS) URL that you generate, so we never need your storage account keys.

Grant CloudMailin permission to send email to your Azure Container

1. Create a new Container in the Blob service panel of your Azure Storage Account (or choose an existing one).
2. Go to Settings and then Shared Access Signature (SAS).
3. Generate a SAS URL for the Blob service with Object and Write permission and select the start and end dates for the signature. You'll need a large enough date range to provide CloudMailin continued access to the container.
4. Once you've generated the URL save a copy of the full SAS URL. CloudMailin needs the whole URL, not just the SAS token.

Be sure to select a large enough date range for continued use with CloudMailin.

You should now have granted CloudMailin permission to add files to your Azure Blob Storage container. You can now Setup CloudMailin to receive the emails in its Webhook.

Send the full email to Google Cloud Storage

It's possible to configure CloudMailin to send the full email directly to a Google Cloud Storage bucket. You grant the CloudMailin upload service account permission to create objects in your bucket, so there are no credentials to share with us.

Grant CloudMailin permission to send email to your Google Cloud Storage Bucket

1. Head to the Google Cloud Platform management page and go to Storage.
2. Create a new Bucket or edit your existing bucket.
3. Click on the Permissions Tab and select Add to add a member to the permissions tab.
4. Grant the CloudMailin Service Account (below) Storage Object Creator permission to allow the creation of new Storage Objects.

The CloudMailin service account that you need to grant permission is: uploads@cloudmailin-uploads.iam.gserviceaccount.com

You should now have granted CloudMailin permission to add files to your Google Cloud Storage bucket. You can now Setup CloudMailin to receive the emails in its Webhook.

Setup CloudMailin to Send Emails to Cloud Storage

Now that you've added the permission to upload emails head to CloudMailin and enable the feature.

1. Log into your Address Dashboard and choose the address you wish to manage.
2. Select Add full message storage and choose your storage provider.
3. Enter the details for the provider you set up above:
   • For AWS S3 enter your bucket name and an optional path prefix to place before each file name (in the format bucket_name/path_prefix). You'll also need to add your S3 bucket region and select the permission to apply to files when they are created. We recommend using Bucket owner full control here.
   • For Azure Storage enter the full SAS URL you generated above and the name of the container. CloudMailin extracts the storage account domain and SAS token from the URL.
   • For Google Cloud Storage enter your bucket name and an optional path prefix to place before each file name (in the format bucket_name/path_prefix).
4. Finally, you'll need to select the Format.

When you save, CloudMailin writes a small test file to your storage to check that the permissions are correct. If the test fails the settings are not saved and the form will show which field needs attention.

Now when your emails are received you'll still get the regular Webhook but your HTTP POST will also include the store_url parameter in the envelope. For example the JSON format will look like the following:

"envelope": {
  "to": "to@example.com",
  "from": "from@example.com",
  "helo_domain": "localhost",
  // ...
  "store_url": "https://example.s3.amazonaws.com/2021_12_01_00_00_00_a8ed6a3f7aeb93ce726b9dd2dea9eb53.eml"
}

For more detail relating to the store_url see the HTTP Post Formats documentation.