Email API for Gmail and Outlook

Read, search, send and reply from your users' Gmail and Outlook mailboxes with one REST API. Same requests for both providers, with a webhook for every new message.

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Gmail + Outlook
Webhooks
One API

InboxGET /v1/email/threads

Lena Fischer10:42

Demo on Thursday?Is the 2 pm slot still free?

Contoso Billing09:15

Invoice INV-2041Your January invoice is attached.

Daniel ParkYesterday

Re: Contract draftTwo small edits on page 3.

Priya ShahMon

Offsite agendaSharing the plan for next week.

message.receivedLena Fischer, also in your inbox

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Supported platforms

One API. Gmail and Outlook

Connect a Google or Microsoft account and call the same email endpoints for both

Gmail
Google Calendar
Google Drive
Google Contacts

Gmail, read and send

Threads, labels, attachments and sends from a Gmail or Google Workspace mailbox.

Outlook
Outlook Calendar
OneDrive
Outlook Contacts

Outlook, read and send

Threads, folders, attachments and sends from a Microsoft 365 mailbox.

Explore Microsoft

How it works

From signup to first email in three steps

1

Key name

e.g., Production API key

Permission

Read & write

Read only

Profile access

Full access (all profiles)

Create key

Get your API key

Sign up free and create a key in the dashboard.

2

Profile

Default

Google

emailcalendarfilescontacts

Microsoft

emailcalendarfilescontacts

Connect Google or Microsoft

Request a connect link with the areas you need. Each account gets an ID for API calls.

3

POST /v1/email/messages

curl -X POST "https://zernio.com/api/v1/email/messages" \
  -H "Authorization: Bearer $ZERNIO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "accountId": "acc_xxx",
    "to": [{ "email": "lena@northwind.io", "name": "Lena" }],
    "subject": "Your demo on Thursday",
    "text": "Hi Lena, see you Thursday at 2 pm."
  }'

Send from their mailbox

POST /v1/email/messages sends as the connected user and returns the stored sent copy.

Features

Everything you need for email

Read

Threads and messagesNewest first, cursor paginated
Filters and searchUnread, sender, dates, native query
Folders and labelsGmail labels, Outlook folders
AttachmentsDownload any attachment by ID
Raw and headersFull headers or the raw message

Send

SendTo, cc, bcc, text and HTML
Reply and reply allThreaded by the provider
AttachmentsUp to 20 files, 25 MB in total
Headers and metadataCustom X- headers, your own keys
Send caps1,000 a day on Outlook, 500 on Workspace

Organize and listen

Read stateMark messages read or unread
Star and flagGmail stars, Outlook flags
MoveBetween folders or labels
TrashOne call per message
message.receivedA webhook for each new email

Frequently asked questions

Add Gmail and Outlook to your app

Connect a mailbox, send the first email and get a webhook for every reply.

Start for free Read the docs

Gmail + Outlook
Webhooks
One API