Linking MailerSend as a source

The MailerSend connector syncs your transactional email data – activity events, domains, recipients, and templates – into PostHog, so you can analyze your email data alongside your product data.

Prerequisites

You need a MailerSend account with an API token that has read access to the data you want to sync. MailerSend retains email activity for 1-30 days depending on your plan, so the activity table only backfills as far as that retention window on its first sync.

Adding a data source

1. In PostHog, go to the Sources tab of the data pipeline section.
2. Click + New source and click Link next to this source.
3. Enter your credentials (see Configuration below) and click Next.
4. Select the tables you want to sync, choose a sync method and frequency, then click Import.

Once the syncs are complete, you can start querying this data in PostHog.

When linking MailerSend, you'll need:

• API token – create one in your MailerSend domain settings. Grant the token read access to the data you want to sync, such as Email (for activity events), Domains, Recipients, and Templates.

Sync modes

Each table can be synced in one of several modes, depending on what the source supports:

• Webhook (when available) – the source pushes changes to PostHog in real time. Fastest freshness, lowest ongoing cost, and the only mode that reliably captures updates and deletes.
• Incremental – only new or updated rows are synced on each run, using a cursor field (such as an updated_at timestamp). Cheaper than a full refresh, but deletes aren't captured.
• Append only – new rows are appended using a cursor field; existing rows are never updated. Ideal for immutable, append-only tables like event logs.
• Full refresh – the whole table is reloaded on every sync. Use it when a table has no reliable cursor or when you need deletions reflected.

See sync methods for a full explanation of how each mode works and how to choose between them.

Configuration

Supported tables

The tables available from this source are discovered from your account when you connect it, so the exact list depends on your data. Once connected, you can pick which tables to sync from the sources tab.

Troubleshooting

• If your API token is invalid or has been revoked, create a new token in your MailerSend domain settings, then reconnect.
• If your token is missing the read permissions needed to sync some data, grant the required read scopes in your MailerSend domain settings, then reconnect.

If your sync is failing or data looks wrong, see the Data warehouse troubleshooting guide. If that doesn't help, contact support – we're happy to help.