ImprovMX

ImprovMX is a custom-domain email forwarding service that also supports outbound mail through SMTP and an API. It suits domain owners, small teams, and developers who need programmable routing without operating a mail server. Its strongest advantage is routing flexibility; the main caution is what happens when a domain reaches its forwarding quota.

Overview

ImprovMX routes messages from custom addresses into existing inboxes and can send mail from the same domain. Catch-all and regex aliases, configurable rules, and delivery to multiple destinations make it suitable for anything from a simple domain-wide forwarder to internal tools with more deliberate address handling.

The service has operated since 2013 as a self-funded United States company and says it serves more than 200,000 users and organizations. Free accounts receive API access, while SMTP sending is reserved for paid plans. That split makes the free tier useful for inbound forwarding and automation, but not for applications that need authenticated SMTP delivery.

Key features

Routing and sending

Catch-all forwarding handles addresses across a domain, while regex aliases and routing rules support narrower patterns. One alias can forward to multiple destinations, which is practical when messages must reach both a personal inbox and a team mailbox. Alias and rule limits vary substantially by plan, so complex domains should be sized against those caps rather than assuming unlimited routing.

Sending from a custom domain works through SMTP or the JSON Send API. The REST API also manages domains and aliases programmatically, making it a sensible choice for developers and services that need to update forwarding configuration automatically. SMTP setup guides cover Gmail, Apple Mail, and Thunderbird.

DNS, logs, and operations

Premium users can use one-click DNS setup with supported providers; an update in June 2026 says this now works with most providers. Configuration guides cover services including Cloudflare, Namecheap, DigitalOcean, Vercel, and Netlify, reducing the work involved in connecting a domain.

Delivery logs show the subject, sender, destination, event type, server response, and status code, but not message content. Standard transparency retention is seven days for delivery logs and 365 days for setup-change records; paid tiers extend email-log retention to as much as 180 days or unlimited, depending on the plan. Webhooks are included on Premium.

ImprovMX says it encrypts stored data, uses TLS for SMTP connections that support it, conducts annual independent penetration tests, is GDPR compliant, and does not sell data or log forwarded email content. It does not pursue SOC 2 or ISO 27001 certification, so organizations requiring either certification should look elsewhere.

Quota behavior and support

When a domain reaches its forwarding quota, processing stops until the quota resets at 00:00 UTC. Mail received during the suspension is bounced to senders, not queued for later delivery. That is a material operational risk for busy domains and should be part of any capacity calculation. Free users get standard email and chat support; Premium and Pro add priority support, while Enterprise includes support service-level agreements and a dedicated account manager.

Pricing

Free — free. This tier covers one domain, 25 aliases, 500 forwarded emails per day, seven-day email-log retention, API access, and a 99% uptime guarantee. It is a reasonable starting point for a personal domain or low-volume project, but the daily cap and lack of SMTP sending limit it for active business use.

Premium — $9 a month, billed Monthly. You get up to 30 domains, 100 aliases and 10 rules per domain, 5,000 forwarded emails per day, 12,000 SMTP sends per month, logs retained up to 180 days, webhooks, and priority email and chat support. This is the most balanced paid option for small businesses that need outbound mail and moderate routing complexity.

Pro — $24 a month, billed Monthly. It raises capacity to 100 domains, 200 aliases and 50 rules per domain, 15,000 forwarded emails per day, and 60,000 SMTP sends per month. Choose it when several domains or high-volume application sending make Premium's ceilings restrictive.

Light — $50 a year, billed Yearly. Light supports up to five domains, 25 aliases and five rules per domain, 5,000 forwarded emails per day, and 750 SMTP sends per month. Its annual price is attractive for modest forwarding needs, but the small sending allowance and tighter routing limits make it less suitable for mail-heavy automation.

Enterprise — custom pricing, billed Custom. This plan provides unlimited domains, aliases, forwarding, and SMTP sends, plus a dedicated account manager and support SLAs. It is intended for organizations that need contractual support and no published capacity ceilings.

Platforms

ImprovMX is available through its web interface and API. The documented SMTP setup guides connect it to Gmail, Apple Mail, and Thunderbird, while DNS guides cover major hosted and developer-oriented providers.

Who it's for

Choose ImprovMX for custom-domain owners who want more than basic forwarding, developers managing aliases through an API, and small teams that need SMTP sending alongside inbound routing. It is less appropriate for high-volume domains that cannot tolerate quota-triggered bounces, or procurement processes that require SOC 2 or ISO 27001 certification.

Pros and cons

• Pros: Catch-all, regex, rule-based, and multi-destination routing handle complex address schemes.
• Pros: API access is included on Free, with SMTP and JSON Send options for paid users.
• Pros: Operational logs expose delivery events without storing forwarded message content.
• Cons: Hitting a daily quota stops processing and causes subsequent mail to bounce until the UTC reset.
• Cons: SMTP sending is unavailable on Free, and alias, rule, and send quotas can constrain larger deployments.
• Cons: No SOC 2 or ISO 27001 certification is pursued.

Alternatives

For a broad comparison, see Email Forwarding Services.

Forward Email is the better pick if open-source software and a wider range of client and self-hosted platforms matter, with an Enhanced Protection plan at $3 a month.

Haltman mail-forwarding-core suits users who want free, forwarding-only service with unlimited rules, users, addresses, domains, and emails.

DNSExit Email Forwarding is worth considering for DNSExit-registered domains, which receive free forwarding; its 5 Emails plan costs $6.99 a year.

EForw fits users who prioritize unlimited catch-all aliases on a free domain, while its Personal plan starts at $1.99 a month.

Forward offers a similar free allowance of one domain, 25 aliases, and 500 forwards per day, with a Starter plan from $2 a month.

InboxMail is an alternative for users seeking unlimited aliases alongside mailbox and campaign features on its free tier.

KaiMail is aimed at lower-volume users, with a free plan limited to 300 emails per month and one day of logs.

Mailcast may suit readers who want a free trial, but its free plan does not support sending from the domain.

Verdict

ImprovMX is a strong choice for individuals, developers, and small businesses that need flexible custom-domain routing, API control, and paid SMTP sending without running mail infrastructure. Choose it for its broad routing toolkit and clear operational logs; look elsewhere if quota-triggered bounces, limited free sending, or the absence of SOC 2 and ISO 27001 certification conflicts with your requirements.