MailHog vs MailCatcher
Two older Go and Ruby catchers, both trailing Mailpit on maintenance and HTML rendering.
What matters for teams building autonomous agents
An agent stack treats email as a two-way primitive. Inbound has to arrive as structured JSON a tool call can consume, sends have to be safe to retry when a model loop repeats itself, and every action needs an audit trail. A provider without inbound parsing only solves half the problem.
| Priority | MailHog | MailCatcher |
|---|---|---|
| Inbound parsing | No | No |
| Idempotency keys | No | No |
| Webhooks | No | No |
| Operating since | Not published | Not published |
| Event stream | No | No |
| Best published rate per 1,000 | Tiers not published in comparable form | Tiers not published in comparable form |
| Batch sending | No | No |
| SDKs | None | None |
| Multi-tenant | No | No |
For an agent that reads and writes email running inbound parsing into tool calls and model-generated sends that must not duplicate, the two are level on every priority that can be scored here, so the choice comes down to price and to which product your team would rather operate. That ordering reflects this audience. Weigh the same table differently and the answer changes.
Side by side
| Feature | MailHog | MailCatcher |
|---|---|---|
| Webhooks | No | No |
| SDKs | None | None |
| Multi-tenant | No | No |
| Tagline | Classic local SMTP catcher (unmaintained since 2020). | Tiny Ruby-based local SMTP catcher. |
| Free tier | Free, MIT-licensed | Free, MIT-licensed |
| Starts at | Free | Free |
| Pricing model | self-hosted | self-hosted |
| API | Yes | Yes |
| SMTP | Yes | Yes |
| Templates | none | none |
| React Email | No | No |
| Inbound | No | No |
| Idempotency | No | No |
| Dedicated IP | No | No |
| Deliverability | Not applicable; capture-only. | Not applicable. |
| DX score | 5/10 | 6/10 |
| Best for | Legacy projects already wired to it. | Rails teams already running it in development. |
MailHog
- ›Familiar from years of tutorials and boilerplates
- ›Single Go binary with a Docker image and a chaos-testing mode
- ›No meaningful releases since 2020
- ›HTML and modern CSS rendering trails current email clients
- ›Open issues and pull requests are effectively unattended
MailCatcher
- ›Installs as a Ruby gem, familiar in Rails stacks
- ›SMTP on 1025 with a web UI and JSON API on 1080
- ›Shows HTML, plain text, and raw source per message
- ›Release cadence is slow with little active feature work
- ›Needs a Ruby runtime where Mailpit ships a static binary
- ›HTML rendering trails newer catchers