## Microsoft Graph Api:

#### SDK:
* https://learn.microsoft.com/en-us/graph/sdks/sdk-installation#install-the-microsoft-graph-java-sdk
* Java sdk: https://github.com/microsoftgraph/msgraph-sdk-java
#### Permissions:
* For attachment upload session: `Mail.ReadWrite`
* For email send: `Mail.Send`
#### Scope:
* `https://graph.microsoft.com/.default`
* Need to delete `IMAP` and `SMTP` scopes.
#### Message format:
* https://learn.microsoft.com/en-us/graph/outlook-send-mime-message
* Can be sent as `Json` or `Mime`.
* `Content-Type: application/json` to use JSON format in the request body.
* `Content-Type: text/plain` to use MIME format in the request body.
* We need to send in `Mime` format. Encode the `Mime` content in `base64` and send as request body.
* For attachments set `Content-Transfer-Encoding: base64`.
* **Error:**
* Type: MIME content malformed, missing
* Method: POST, PUT
* Error code: 400
* Error message: Invalid base64 string for MIME content.
##### Attachments:
* Size: upto 150 mb
* Upload size in a single request 3mb.
* For 3+ mb create an upload session and iteratively upload ranges of the file to attach it.
* Attachment properties:
> {
> "contentType": "string",
> "id": "string (identifier)",
> "isInline": true,
> "lastModifiedDateTime": "String (timestamp)",
> "name": "string",
> "size": 1024
> }
* https://learn.microsoft.com/en-us/graph/api/resources/attachment?view=graph-rest-1.0#methods
* https://learn.microsoft.com/en-us/graph/api/attachment-createuploadsession?view=graph-rest-1.0&tabs=http
##### Limits:
* https://learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits#sending-limits
* Emails sent per minute: 30.
* Maximum recipients per email: upto 1000.
#### Send email process:
* Api: `https://graph.microsoft.com/v1.0/me/sendMail`
* Encode entire `Mime message` object with attachments into `Base64` and set as request body.
* Authorization: `Bearer $authToken`
* Method: `POST`