Freedom251 › Email Forwarding Services
KaiMail
What KaiMail is
KaiMail provides email forwarding and sending with customers’ custom domains. Incoming messages can be forwarded to an existing inbox with ARC and DKIM signing, or sent to an endpoint as structured JSON through HTTP POST. Webhook requests carry an HMAC-SHA256 signature, delivery is retried with exponential backoff if an endpoint is down, and attachments are supplied through signed URLs. An HTTPS API sends email from a custom domain and returns delivery tracking IDs and status checks. It authenticates with HTTP Basic Auth using existing SMTP credentials, rather than separate API keys. Webhook events can be connected to ticketing systems, Slack notifications, CRM updates, and other HTTP actions. KaiMail lists TLS encryption in transit, account access controls, and regular security reviews. Email logs are kept for up to 61 days and webhook attachments for seven days by default. The free plan supports one custom domain, one mailbox, and up to 300 emails per month. Paid plans cost ¥550 a month, ¥1,650 a month, or ¥5,500 a month. The service is available on the web and through an API.
Who it suits
KaiMail suits developers and teams that want custom-domain forwarding or sending and can handle DNS configuration and webhook setup. Its terms say those tasks require technical knowledge.
What it does well
- Forwards incoming email with ARC and DKIM signing.
- Webhook delivery includes signatures and retries.
- Sending API provides tracking IDs and status checks.
- Free plan includes one domain and mailbox.
- Supports email events sent to HTTP endpoints.
What to know first
- Free plan is limited to 300 emails monthly.
- Support is provided exclusively via email.
- DNS and webhook setup require technical knowledge.
- Webhook attachments are retained for seven days by default.
Limits
KaiMail Basic is free and limited to one custom domain, one mailbox, 300 emails per month, a 1 MB maximum email size, and one day of log retention. SMTP sending is included in the listed paid plans, starting with KaiMail Plus at ¥550 a month, including tax.
Plans
| Plan | Billed and limits | Price |
|---|---|---|
| KaiMail Basic | Free · 1 custom domain · 1 mailbox · 300 emails/month max · 1MB max email size · 1 day logs retention | Free |
| KaiMail Pro | ¥1650 /month (inc. tax) · 10 custom domains · 20 mailboxes · 10k emails/month max · 25MB max email size · 30 days logs retention · SMTP sending (1,000/month) | ¥1,650 a month |
| KaiMail Plus | ¥550 /month (inc. tax) · 2 custom domains · 5 mailboxes · 5k emails/month max · 10MB max email size · 7 days logs retention · SMTP sending (500/month) | ¥550 a month |
| KaiMail Business | ¥5500 /month (inc. tax) · 50 custom domains · Unlimited mailboxes · 50k emails/month max · 35MB max email size · 30 days logs retention · SMTP sending (2,000/month) · Priority support | ¥5,500 a month |
As kaimail.net lists them, read 8 Oct 2026. The maker's own page has the final word.
Getting started
- Visit kaimail.net.
- Configure DNS for the custom domain.
- Choose KaiMail Basic or a paid plan based on domain, mailbox, email volume, size, and log needs.
- Set up forwarding to an inbox or configure an HTTP POST webhook endpoint.
- For outbound sending, use the HTTPS API with existing SMTP credentials.
Verdict
KaiMail combines custom-domain forwarding, webhook delivery, and API-based sending. Check the plan limits and technical setup requirements against the volume and integrations you need.
Questions
Is KaiMail free?
Yes. KaiMail Basic is free and includes one custom domain, one mailbox, up to 300 emails per month, a 1 MB maximum email size, and one day of log retention.
What do the paid plans cost?
KaiMail Plus costs ¥550 a month, KaiMail Pro costs ¥1,650 a month, and KaiMail Business costs ¥5,500 a month. Each listed amount is billed monthly and includes tax.
Which platforms does KaiMail support?
KaiMail lists web and API as its platforms.
Can KaiMail send email as well as forward it?
Yes. Its HTTPS API sends email from a custom domain and provides tracking IDs and status checks. The API authenticates with HTTP Basic Auth and existing SMTP credentials.
What integrations are described?
Webhook events can connect to ticketing systems, Slack notifications, CRM updates, and other HTTP actions.
How long are email logs and webhook attachments retained?
The privacy policy says email logs are retained for up to 61 days. Webhook attachments are retained for seven days by default.
Facts from KaiMail's own pages
- API authentication
- The HTTP sending API uses HTTP Basic Auth with existing SMTP credentials, so separate API keys are not required. · kaimail.net, 8 Oct 2026
- Data retention
- The privacy policy says email logs are retained for up to 61 days and webhook attachments for 7 days by default. · kaimail.net, 8 Oct 2026
- Forwarding
- Email is forwarded to an existing inbox with ARC and DKIM signing. · kaimail.net, 8 Oct 2026
- HTTP sending
- KaiMail offers an HTTPS API for sending email from a custom domain, with delivery tracking IDs and status checks. · kaimail.net, 8 Oct 2026
- Integrations
- The webhook page describes connecting email events to ticketing systems, Slack notifications, CRM updates, and other HTTP actions. · kaimail.net, 8 Oct 2026
- Intended users
- KaiMail describes itself as developer-first email forwarding for developers and teams. · kaimail.net, 8 Oct 2026
- Product
- KaiMail provides email forwarding and sending using customers’ own custom domains. · kaimail.net, 8 Oct 2026
- Security
- The privacy policy lists TLS encryption in transit, ARC/DKIM email authentication, account access controls, and regular security reviews. · kaimail.net, 8 Oct 2026
- Support
- The terms state that support is provided exclusively via email. · kaimail.net, 8 Oct 2026
- Technical requirements
- The terms say DNS configuration for custom domains and webhook integration require technical knowledge. · kaimail.net, 8 Oct 2026
- Webhook attachments
- Attachments are delivered alongside the JSON payload through signed URLs. · kaimail.net, 8 Oct 2026
- Webhook delivery
- Incoming emails can be delivered to an endpoint as structured JSON using HTTP POST. · kaimail.net, 8 Oct 2026
- Webhook retries
- KaiMail retries webhook delivery with exponential backoff when an endpoint is down. · kaimail.net, 8 Oct 2026
- Webhook security
- Webhook requests include an HMAC-SHA256 signature for authenticity verification. · kaimail.net, 8 Oct 2026
Where KaiMail stands on Freedom251
- Email Forwarding Services#9 of 25