---
title: "Configure Mastodon to send email over SMTP"
description: "SMTP_* in .env.production with SMTP_ENABLE_STARTTLS=always on 587, then restart Sidekiq."
url: https://www.unitpost.com/docs/smtp/mastodon
section: SMTP
updated: 2026-11-02
---
# Configure Mastodon to send email over SMTP

## Connection settings

- **Host**: smtp.unitpost.com
- **Username**: unitpost (always this literal value)
- **Password**: Your Unitpost API key (must carry emails:send)
- **Port (STARTTLS)**: 587 (or 2587 if blocked, or 25)
- **Port (implicit TLS)**: 465 (or 2465 if blocked)
- **Security**: TLS 1.2 or 1.3 (required before AUTH)
- **From address**: Any address on a verified domain

## Configure Mastodon to send email over SMTP

> SMTP_* in .env.production with SMTP_ENABLE_STARTTLS=always on 587, then restart Sidekiq.

Mastodon sends sign-up confirmations, password resets and notification emails from its Sidekiq workers, using the `SMTP_*` variables in `.env.production`. `SMTP_FROM_ADDRESS` falls back to `notifications@localhost`, which Unitpost rejects, so set it to an address on your verified domain.

### 1. Create a send-only key

In Unitpost, open Settings → SMTP and create a send-only key. Verify the domain (/docs/domains) you'll use in `SMTP_FROM_ADDRESS`.

### 2. Set the SMTP variables

Edit `.env.production` in the Mastodon directory. `SMTP_ENABLE_STARTTLS=always` requires the upgrade on 587; the default `auto` only tries it when offered.

```env
SMTP_SERVER=smtp.unitpost.com
SMTP_PORT=587
SMTP_LOGIN=unitpost
SMTP_PASSWORD=pk_live_...
SMTP_AUTH_METHOD=plain
SMTP_ENABLE_STARTTLS=always
SMTP_FROM_ADDRESS=notifications@yourdomain.com
```

> For port 465, use `SMTP_PORT=465` and `SMTP_TLS=true`, and remove `SMTP_ENABLE_STARTTLS`: STARTTLS and implicit TLS can't be on together.

### 3. Restart Sidekiq and reload the web process

Sidekiq delivers the mail, so it has to restart to load the new values. The web process reloads without downtime.

```bash
sudo systemctl restart mastodon-sidekiq
sudo systemctl reload mastodon-web
```

### 4. Send a test

A running server has no test button. Sign out and use Forgot your password? on the sign-in page with an account whose inbox you can read. On a fresh install, `RAILS_ENV=production bin/rails mastodon:setup` offers to send a test email after its SMTP questions.

### 5. If nothing arrives

Failed deliveries wait as retries in the Sidekiq dashboard at `/sidekiq`, with the SMTP reply. `550 5.7.1` means `SMTP_FROM_ADDRESS` isn't on a verified domain; `535 5.7.8` means `SMTP_LOGIN` isn't `unitpost`.

## Related

- [Nextcloud SMTP settings for the email server](https://www.unitpost.com/docs/smtp/nextcloud): Basic settings → Email server or the mail_* keys in config.php; the From address is split in two.
- [Configure Directus email over SMTP](https://www.unitpost.com/docs/smtp/directus): EMAIL_TRANSPORT=smtp and EMAIL_SMTP_* variables; EMAIL_SMTP_SECURE means port 465, not STARTTLS.
- [Set up SMTP for self-hosted Appwrite](https://www.unitpost.com/docs/smtp/appwrite): _APP_SMTP_* in the install's .env with _APP_SMTP_SECURE=tls for 587, then docker compose up -d.