Engineering Blog

Guides, updates, and deep dives on email infrastructure.

Practical advice from the team that's been building email tools for developers since 2010.

A fresh new look for CloudMailin
Changelog

A fresh new look for CloudMailin

We've started rolling out a refreshed design for CloudMailin. The new look lands first across our public site and sign-up flow, with the rest of the dashboard following over the coming weeks.
Profile Image: Steve Smith Steve Smith 29 May 2026
Changelog

New: Markdown support for outbound email

You can now send outbound email using Markdown. Set the markdown parameter when sending via the API and we'll render it to both HTML and a simplified plain text version for you.
Profile Image: Steve Smith Steve Smith 4 Mar 2026
Changelog

Outbound pipeline performance improvements

We're making a number of performance improvements to the outbound email pipeline. We'll share more details as we roll out further improvements.
Profile Image: CloudMailin Team CloudMailin Team 4 Mar 2026
Changelog

Automatic brand colours for outbound email templates

When setting up an outbound email template you can now enter your website URL and we'll automatically extract your brand colours and logo. These are then applied to your email template so your transactional emails match your brand out of the box.
Profile Image: Steve Smith Steve Smith 26 Feb 2026
Changelog

Updated inbound and outbound API documentation

We've updated our inbound and outbound API documentation to use the live API description. This ensures that our docs are always up to date with the latest endpoints, parameters and response formats.
Profile Image: CloudMailin Team CloudMailin Team 20 Feb 2026
Changelog

Attachment URLs in full email JSON

Many of our users offload inbound email processing to serverless functions like AWS Lambda, Google Cloud Functions or Azure Functions using our cloud storage providers to store the full message.
Profile Image: CloudMailin Team CloudMailin Team 11 Feb 2026
Header Image Email Authentication with DMARC: A Complete Guide for 2026
dmarc

DMARC Authentication Guide

When a spammer sends email pretending to be from your domain, it damages your reputation and puts your customers at risk. Even though you never sent the message, recipients associate the phishing attack with your brand. These spoofing attacks cost businesses millions annually in lost revenue, damaged relationships, and eroded customer trust.
Profile Image: CloudMailin Team

CloudMailin Team

6 Feb 2026
Changelog

New: Outbound Messages API

In a previous update we started returning UUIDs in the inbound SMTP response. Inbound messages now include this UUID in the API response too, making it easier to correlate messages across your systems.
Profile Image: CloudMailin Team CloudMailin Team 5 Feb 2026
Changelog

Inbound SMTP now responds with UUID

CloudMailin's inbound SMTP servers now respond with a UUID instead of an integer when accepting email. For example, the response will now be:
Profile Image: CloudMailin Team CloudMailin Team 1 Dec 2025
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Curious Windows-1258 Encoding Errors

We initially dismissed the bug reports. A handful of customers were seeing client_error responses when forwarding emails through CloudMailin—the telltale sign of an email encoding error that asks customers to contact support. The emails were marked as Windows-1258, the Vietnamese code page, but customers told us they didn't have any Vietnamese users. The volume was tiny, so we set it aside.
Profile Image: Steve Smith

Steve Smith

26 Nov 2025
Changelog

Failed email deliveries now visible in dashboard

You can now see when email deliveries fail and view the associated error messages directly in your dashboard. Previously these errors were only visible in the SMTP / API responses.
Profile Image: CloudMailin Team CloudMailin Team 20 Sep 2025
claude

CloudMailin MCP - Let AI interact with your CloudMailin Email Address

MCPs are an interesting new development in the world of AI and Large Language Models (LLMs). MCPs give you an API to make calls from your LLM to an external service. The CloudMailin MCP allows you to interact with your CloudMailin email address from your LLM.
Profile Image: Steve Smith

Steve Smith

22 May 2025
Header Image Receiving email attachments in S3 compatible storage
email

Receiving email attachments in S3 compatible storage

CloudMailin can now send email attachments directly to Amazon AWS S3 compatible stores such as Digital Ocean Spaces, Cloudflare R2, Wasabi, MinIO and more.
Profile Image: CloudMailin Team

CloudMailin Team

19 Mar 2025
Changelog

Set the format for Heroku Addresses

We've added a new option to the Heroku addon to allow you to set the format for the address as you provision it.
Profile Image: CloudMailin Team CloudMailin Team 21 Feb 2025
Changelog

Test Mode for SMTP

We've extended the test_mode feature for outbound SMTP to allow you to test your outbound SMTP configuration without actually sending the email.
Profile Image: CloudMailin Team CloudMailin Team 5 Nov 2024
Changelog

Send email attachments to AWS S3, Azure or Google Storage

Today we're excited to announce that all storage providers are now available for both attachments and full message storage.
Profile Image: CloudMailin Team CloudMailin Team 25 Sep 2024
Header Image Announcing Email Layouts (Beta): Best Practice Responsive Email Designs
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Announcing Email Layouts (Beta)

Unlock the full potential of your transactional email campaigns with CloudMailin's responsive layouts (Beta). Our best practice email designs allow you to get started sending professional, well-designed, and mobile-friendly emails effortlessly.
Profile Image: CloudMailin Team

CloudMailin Team

20 Sep 2024
Changelog

DMARC Report Alpha

We're excited to announce that we're launching an alpha of our DMARC analytics service. DMARC Reports let ISPs report back on who is sending email on your behalf. This can help you identify any unauthorized senders and improve your email deliverability.
Profile Image: CloudMailin Team CloudMailin Team 4 Jun 2024
Changelog

Absolute email status times

Our latest dashboard has been released using UTC time as the default for all inbound and outbound email statuses. This makes it easier to find details of historic email events. However, should you wish to change back to the relative time you can simply click the clock icon to switch.
Profile Image: CloudMailin Team CloudMailin Team 28 May 2024
Changelog

Realtime updates for dashboard

Our latest dashboard has been released with a new real-time update for emails sent and received. Working with CloudMailin to send emails should be easier than ever.
Profile Image: CloudMailin Team CloudMailin Team 28 May 2024
Changelog

Set DKIM Records with a CNAME (Beta)

CloudMailin has used 2048 bit keys for DKIM records for some time now as we're committed to providing the best security for our customers. However, the process of adding these records to your DNS can be a little tricky.
Profile Image: CloudMailin Team CloudMailin Team 22 Apr 2024
Header Image What is a transactional email a 2024 review?
reputation

What is transactional email?

What is transactional email and does it compare to other types of email? Next we'll discuss maximising email deliverability and what makes the best transactional email platform.
Profile Image: CloudMailin Team

CloudMailin Team

30 Mar 2024
Changelog

Fixed: email attachment encoding with text/* content type

We've fixed a small issue where attachments with a text/* content type were being encoded incorrectly. This was causing some characters to be displayed incorrectly once stored.
Profile Image: CloudMailin Team CloudMailin Team 28 Mar 2024
Changelog

New: email attachments via the API

It's now possible to set attachments via the API when creating a new address. Please see the API documentation for more detials.
Profile Image: CloudMailin Team CloudMailin Team 20 Mar 2024
Changelog

New: deliverability tests check DMARC, DKIM, SPF

We've added a tool to let customers check deliverability of their emails. You can check any sent email for DMARC, DKIM and SPF records that are correctly setup just by sending to a CloudMailin address.
Profile Image: CloudMailin Team CloudMailin Team 8 Feb 2024
Header Image Receive Email with Python and Django in 2023 (Updated Examples)
python

Receive email with Python and Django in 2023

CloudMailin allows you to receive any volume of email from within your website or application. Although we've had example code showing receiving email with Python for some time the examples needed a refresh to bring them up to date. We've just updated our just updated our documentation to include examples of receiving email in Python with Flask and Django.
Profile Image: Steve Smith

Steve Smith

25 Sep 2023
Changelog

See received email attachment details in the dashboard

We've added a new feature to the dashboard that lets you see details of attachments received with inbound emails. This is useful for debugging and understanding the content of emails that are sent to your CloudMailin address.
Profile Image: CloudMailin Team CloudMailin Team 21 Sep 2023
Header Image New email message previews for CloudMailin outbound sent email
email

New email previews for sent email

We are excited to announce that CloudMailin now allows you to preview sent email messages whether they were sent via SMTP or our Email API.
Profile Image: CloudMailin Team

CloudMailin Team

1 Sep 2023
Changelog

New: added outbound email message previews

It's now possible to see previews of outbound emails that have been sent. A blog post with more details is coming soon.
Profile Image: CloudMailin Team CloudMailin Team 20 Aug 2023
Header Image How to receive email with Next.js, the app router and Typescript
nextjs

Receive email with Next.js

Next.js is a React framework that allows you to build static and server-side rendered applications. In this article, we'll explore how to send and receive email using CloudMailin and Next.js's API routes written in Typescript.
Profile Image: Steve Smith

Steve Smith

4 Aug 2023
Header Image How to Receive Email with Supabase and Typescript
supabase

Receive email with supabase

Supabase is an open-source database, authentication system, and hosting platform that allows developers to quickly and easily build powerful web-based applications. It provides an API that enables developers to connect, query, and manage data on their web projects and mobile applications.
Profile Image: Steve Smith

Steve Smith

12 May 2023
Header Image Now your team can manage your Email API
teams

Now your team can manage your Email API

For over 12 years CloudMailin has provided our customers with the ability to receive email via API as a webhook. In recent years we've also added an outbound email API that allows customers to send transactional email via HTTPS (or send messages via SMTP), making inbox delivery clear and simple.
Profile Image: CloudMailin Team

CloudMailin Team

16 Nov 2022
Header Image Sending and receiving email in Go (GoLang) in 2023 with CloudMailin
golang

Sending and Receiving email in Go

There are multiple ways to send and receive email with Go (Golang). In this article we'll take a look at a couple of them and why we think using HTTP is actually a great method vs SMTP, IMAP and POP3.
Profile Image: CloudMailin Team

CloudMailin Team

12 Apr 2022
Header Image What is a webhook and how does email to webhook work?
webhooks

What are email webhooks?

In this article we discuss webhooks, what they are and how you can use webhooks for both email to webhook and sending email events.
Profile Image: CloudMailin Team

CloudMailin Team

24 Jan 2022
Header Image Encrypted Full Email Storage / Backup API for AWS S3, Google Cloud Storage, Azure Blob
aws

Full Email Storage / Backup API

CloudMailin allows you to store or backup an entire email in either EML format or fully parsed JSON. Full Emails are stored within an AWS S3 bucket, Azure Blob Storage or Google Cloud Storage and delivered to your webhook, creating an encrypted backup with API for your web application.
Profile Image: CloudMailin Team

CloudMailin Team

16 Nov 2021
Header Image Which SMTP port should I use in 2021? SMTP Email Port 25 vs 465 vs 587 vs 2525?
smtp

Which SMTP port should I use for sending email?

Learn the difference between the main SMTP client and server ports (Port 25, 465, 587 and 2525), which one you should choose, what Start TLS is, and why you shouldn't use port 25 to send email messages.
Profile Image: CloudMailin Team

CloudMailin Team

15 Oct 2021
Header Image Receiving Email Attachments in AWS S3 is changing
aws

HTTPS Links for S3 Attachments

CloudMailin allows you to receive email attachments directly to Cloud Storage such as AWS S3. Starting Oct 15 2021 these links will use HTTPS.
Profile Image: CloudMailin Team

CloudMailin Team

1 Oct 2021
Header Image Using TypeScript with AWS Lambda and SAM
aws

TypeScript and AWS Lambda?

In this article, we'll discuss how to get TypeScript working with AWS Lambda and AWS SAM in just a few easy steps.
Profile Image: Steve Smith

Steve Smith

27 Aug 2021
Header Image What is AWS SAM? Building an HTTP API with Amazon Web Services Serverless Application Model and Lambda
aws

Building an HTTP API with AWS SAM and Lambda

In this article, we cover what AWS SAM is, how to get started and how it helps deploy serverless applications and Lambda functions to Amazon Web Services. We'll use JavaScript here, but AWS supports a range of languages.
Profile Image: Steve Smith

Steve Smith

12 Aug 2021
Header Image Sending and receiving email in Node.js and TypeScript in 2023 with CloudMailin
node

Sending and Receiving email in Node.js

In this article, we'll cover a couple of ways to send email in Node.js and TypeScript. Following this we'll outline a quick and easy way to receive email with CloudMailin.
Profile Image: CloudMailin Team

CloudMailin Team

12 Mar 2021
Header Image Receiving email attachments with Google Cloud Storage
google

Email attachments with Google Cloud Storage

CloudMailin can parse the attachments from email and send the email attachment to Google Cloud Storage automatically.
Profile Image: CloudMailin Team

CloudMailin Team

29 Dec 2020
Header Image Using Basic Authentication with AWS API Gateway and Lambda
aws

Basic Auth with AWS API Gateway & Lambda

Basic authentication is one of the oldest and simplest ways to authenticate HTTP Traffic. Although it has been superseded by a range of different options it's still one of the easiest and most convenient methods, as long as you're using HTTPS.
Profile Image: CloudMailin Team

CloudMailin Team

3 Nov 2020
Header Image Receiving email attachments with Azure blob storage
azure

Email attachments with Azure

CloudMailin allows you to receive emails via an HTTP POST, essentially sending email to a webhook.
Profile Image: CloudMailin Team

CloudMailin Team

10 Jul 2020
Header Image Upgrading the TLS minumum version to TLSv1.2
deprecate

Email encryption upgrade

Security has always been a priority for us at CloudMailin. As an email service provider it's often necessary for us to balance customer requirements and usability and where possible we always give our users a choice. For a while now we've supported both TLS 1.2 and TLS 1.3 on our platform, but we've also allowed connections from servers using TLS versions lower than this if the customer requests it.
Profile Image: CloudMailin Team

CloudMailin Team

1 Jul 2020
Header Image Deprecating our original format
deprecate

Deprecating the original format

When we first started over 10 years ago our original HTTP Webhook format was our only option. The original HTTP Format was a multipart/form-data format that was opinionated, it made a lot of decisions about how you might use it.
Profile Image: CloudMailin Team

CloudMailin Team

21 May 2020
Header Image What is DMARC?
dkim

What is DMARC?

Looking for a comprehensive implementation guide? This post provides a quick DMARC reference. For an in-depth guide covering setup, policy progression, report analysis, and best practices for 2026, see Email Authentication with DMARC: A Complete Guide for 2026.
Profile Image: CloudMailin Team

CloudMailin Team

20 May 2020
Header Image What are DKIM and SPF and how do we use them?
dkim

What are DKIM and SPF?

Sender Policy Framework (SPF) and DomainKeys Identifier Mail (DKIM) are both methods of identifying email senders.
Profile Image: CloudMailin Team

CloudMailin Team

4 May 2020
Header Image Understanding Email Reputation
reputation

Understanding Email Reputation

Email sender reputation is crucial when sending an email. Since the early 1990s people have been sending Unsolicited Bulk Email or SPAM and it's critical you understand how to check and manage your reputation.
Profile Image: CloudMailin Team

CloudMailin Team

17 Apr 2020
Header Image Automatically uploading email attachments to Amazon S3
aws

Email attachments with AWS S3

For a while now CloudMailin has allowed you to send your attachments to S3. We call this feature attachment stores, but what exactly does this mean?
Profile Image: CloudMailin Team

CloudMailin Team

1 Mar 2020

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