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SES Mailer

Demonstrates how to send email faster using AWS SES without a backend.

How it works

SES Mailer uses lambda to send mass email. It is invoked by S3 PUT event when a mailing list is dropped into the designated bucket. The function takes its message content from a HTML and plain text message file dropped in the same bucket. It sends multipart/alternative formatted emails.


  1. Deploy on AWS Lambda with a timeout setting of 5 minutes. Make sure the lambda Role has S3 read/write permissions to the bucket and ses:SendRawEmail permission. Configure Lambda environment variables e.g REGION=us-east-1, MAX_THREADS=10, TEXT_MESSAGE_FILE=email_body.txt, HTML_MESSAGE_FILE=email_body.html

  2. Create a S3 bucket and set put event to trigger this lambda function.

  3. In the S3 events configuration, set the event suffix to .gz.

  4. Write your html formatted email in file html_message.html and upload to S3 bucket.

  5. Write the plain text version of your email message in file text_message.txt and upload to S3 bucket.

  6. Create a mailing list file i.e mailing_list_14032016.csv with contents in the below csv format. Don't include first row as header fields.

    Sender Name <>, Recipient Name <>, subject
  7. Compress the file using gzip. e.g gzip -kf mailing_list_14032016.csv creates mailing_list_14032016.csv.gz

  8. Upload the gzipped file mailing_list_14032016.csv.gz to the S3 bucket and it will trigger this lambda function.

  9. This function will start sending email to all addresses in the csv file and log failures in <FILENAME>_error.log.

Tip: You can send even faster by splitting email list into multiple smaller csv files when the number of addresses exceed over a few 100,000s or increase MAX_THREADS environment variable value to something higher depending on your SES TPS limit.

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