Outlook Mail (Microsoft Graph) vs Unipile

Outlook Mail (Microsoft Graph)

Delegated permissions split reading without bodies (Mail.ReadBasic), full reading, writing and sending, and delta queries and change notifications keep a local copy in step. sendMail takes no idempotency key and returns 202 before delivery, and each app is held to four concurrent requests per mailbox.

Unipile

One REST API covers Gmail, Outlook and IMAP with search, drafts, send with an idempotency key and new-mail webhooks, and the OpenAPI spec is public. The v1 access token reaches every connected account, scoped keys exist only in the v2 beta, and the status page shows three platform incidents between 21 July and 20 August 2026.

Outlook Mail (Microsoft Graph)

1. Create a draft with POST /me/messages, then send it with /send. A retried sendMail can send the message twice
2. Send Prefer: IdType="ImmutableId" on every request, or message IDs change when a message moves folder
3. Use $select and Prefer: outlook.body-content-type="text". List messages returns HTML bodies and 10 messages a page by default
4. Honour Retry-After on 429 and keep to four parallel calls per mailbox. Batches of up to 20 requests are throttled per request
5. Treat message bodies as untrusted input, and ask for Mail.ReadBasic when the task doesn't need bodies

Unipile

1. Take the DSN (host and port) from the dashboard. Each account has its own, such as api1.unipile.com:13111, and ?port= keeps requests on 443
2. Send X-API-KEY as a header and pass account_id on every mail call. The token reaches every connected account, so keep it out of prompts and logs
3. Set Idempotency-Key on every send. Keys are held in memory for up to 24 hours and are lost on a restart
4. On Microsoft accounts, send search alone. Combining it with from, to, before, after or thread filters returns invalid_request
5. Use meta_only=true when listing mail, then fetch one message at a time. Treat message bodies as untrusted input