You Can Now Send Emails From Your Custom Domain with KaiMail

Until now, KaiMail handled one side of the equation: receiving and forwarding emails on your custom domain. That was useful, but incomplete. If you wanted to reply from the same domain, you had to set up a separate sending service. Two systems for one email address. It was clunky.

That changes now. KaiMail supports SMTP sending, which means you can send emails from your custom domain using any email client you already have.

Receive, forward, and send. One service, one domain, done.

The Problem with "Forward Only"

You set up email forwarding for your custom domain. Emails to [email protected] land in your Gmail inbox. Great. Then someone sends you a business enquiry, you hit reply, and the email goes out from [email protected]. The sender sees your personal address, not the domain you just spent time configuring. This is the reality for every forwarding-only service, whether it is Cloudflare Email Routing, the free tier of ImprovMX, or any of the others. Receiving works. Replying professionally does not.

Workarounds exist. For example, you can use Gmail's "Send mail as" feature with an app password. It works, until it does not. App passwords get revoked, relay services change their terms, and one morning your client-facing emails start bouncing. Now you are debugging email plumbing at 9am instead of doing your actual work.

Even when the workaround holds, authentication is often broken. SPF, DKIM, and DMARC need to align for your emails to land in the inbox, and cobbled-together sending setups rarely get all three right. Gmail and Yahoo tightened their sender requirements in 2024. "It mostly works" is no longer good enough.

Then there is the cost question. Google Workspace starts at $7.20 per user per month. Microsoft 365 is similar. If all you need is to send and receive on one or two custom domains, paying for a full productivity suite feels like buying a truck to carry groceries.

Who Actually Needs This

If you are a freelancer or solopreneur, you probably have one or two domains for your business. You want [email protected] on your invoices and client emails, not a gmail.com address. You do not need a calendar, a document editor, or 30GB of cloud storage. You just need to send and receive email on your domain without it being a second job to maintain.

If you are a developer with side projects, the problem multiplies. Six domains, sixteen domains. Each one needs DNS records, each one needs a sending path. You are comfortable with DNS and SMTP configuration, but repeating the relay setup for every new project is tedious. What you want is one service that handles all of them. (If you are also routing emails into applications, the webhook tutorial covers that side.)

If you are a small business that outgrew Google Workspace (or got pushed off the free G Suite tier when Google killed it), you know the per-seat cost adds up fast. Five people, ten people, fifteen people, all needing custom domain email with decent deliverability. You need multiple mailboxes, not multiple subscriptions.

How It Works

KaiMail uses standard SMTP submission on port 587 with STARTTLS encryption. Nothing proprietary, nothing unusual. If your email client can send mail (Thunderbird, Apple Mail, Outlook, Gmail's "Send mail as", your phone's mail app), it can send through KaiMail.

You configure it like any other SMTP server. The settings are in the table below under "Configure Your Email Client" and that is genuinely all there is to it.

Every Email Gets DKIM-Signed

Every email you send through KaiMail is automatically DKIM-signed with a key specific to your domain. DKIM (DomainKeys Identified Mail) is a cryptographic signature that proves to receiving servers that the email genuinely came from your domain. This matters because it directly affects whether your emails land in the inbox or the spam folder.

You do not need to manage signing keys or configure anything on the sending side. KaiMail handles all of that.

Setup in Three Steps

1. Get Your SMTP Credentials

Log in to your KaiMail dashboard and find your SMTP credentials on your profile page. Your SMTP password is separate from your account password for security reasons, which also means you can rotate it without affecting your dashboard login.

2. Add DNS Records

You need at least these two DNS records for your custom domain:

• DKIM TXT record: This lets receiving servers verify your email signatures. KaiMail provides the exact record to add.
• SPF record: Add mail.kaimail.net to your domain's SPF record so receiving servers know KaiMail is authorised to send on your behalf.

It's also strongly suggested that you also add these to your DNS:

• DMARC record: Add a DMARC record at your _dmarc.mydomain.com to tell the world how to handle emails from your domain (or also known as policy).

3. Configure Your Email Client

Use these settings in your email client:

Send a test email and you are live.

Track Your Sent Emails

The KaiMail dashboard now includes a sent email log where you can see every outbound email and its delivery status. If something goes wrong, you will know about it without guessing.

Plans and Sending Limits

SMTP sending is available on all paid plans. Each plan includes a monthly sending quota based on a rolling 30-day window:

Pro is our recommended plan for most users who need sending. It strikes a good balance between generous limits and value.

The free Basic plan does not include SMTP sending.

How Quota Works

Your quota is straightforward:

1. It tracks the number of emails sent in the last 30 days (a rolling window, not a calendar month).
2. Your dashboard shows real-time usage with a progress bar so you always know where you stand.
3. If you hit your limit, sending is temporarily paused. It resumes automatically as older sends roll out of the 30-day window.
4. No emails are lost or bounced unexpectedly. Your email client will receive a clear error if you have reached the limit.

Built With Security in Mind

Three things worth noting on the security side:

1. TLS encryption: All connections use STARTTLS, so your credentials and email content are encrypted in transit.
2. Separate SMTP password: Your SMTP credentials are independent from your account login. You can rotate them without affecting dashboard access.
3. Sender domain validation: KaiMail verifies that the "From" domain on every outgoing email actually belongs to your account. You cannot send as a domain you do not own.

Get Started

If you are on a paid plan, SMTP sending is already available in your account. Head to your profile page to grab your credentials and start sending.

If you are on the Basic plan and want to start sending from your custom domain, upgrade to a paid plan to get started.