Docker

The Papercut SMTP Service runs as a Linux container — ideal for docker-compose dev environments and CI pipelines.

Quick Start

docker run -d --name papercut \
  -p 8080:8080 -p 2525:2525 \
  changemakerstudiosus/papercut-smtp:latest

Web UI: http://localhost:8080
Send email to: localhost:2525

Container ports

The container uses non-privileged ports by default: SMTP 2525 and HTTP 8080. Map them however you like — e.g. -p 25:2525 if your app insists on port 25.

Docker Compose

services:
  papercut:
    image: changemakerstudiosus/papercut-smtp:latest
    ports:
      - "8080:8080"
      - "2525:2525"

  myapp:
    build: .
    environment:
      # inside the compose network, use the service name as SMTP host
      Smtp__Host: papercut
      Smtp__Port: "2525"
    depends_on:
      - papercut

Other containers on the same network reach Papercut at host papercut, port 2525.

Configuration via Environment Variables

Any setting can be overridden with environment variables:

docker run -d \
  -e SmtpServer__Port=2525 \
  -e Urls=http://0.0.0.0:8080 \
  -e HttpPathPrefix=/webmail \
  -p 8080:8080 -p 2525:2525 \
  changemakerstudiosus/papercut-smtp:latest

For TLS in Docker, see TLS & Authentication.

More

Full Docker documentation — volume persistence, Kubernetes examples, and troubleshooting (including volume permission errors) — lives on the Docker Hub page.

.NET Aspire

For Aspire projects, skip raw Docker and use the community integration — CommunityToolkit.Aspire.Hosting.PapercutSmtp:

var papercut = builder.AddPapercutSmtp("papercut");

builder.AddProject<Projects.MyApp>()
    .WithReference(papercut)
    .WaitFor(papercut);

Papercut appears in the Aspire dashboard with auto-assigned ports and a connection string of the form endpoint=smtp://<host>:<port>.

Tag	Meaning
`latest`	Latest stable release
`X.Y.Z` / `X.Y`	Specific stable versions
`dev`	Latest development build