JSON API

JSON API reference

One endpoint, four functions, authentication by header. This is the interface most integrations use, including our own WordPress plugins.

Endpoint

POST https://heb.mesereser.com/Services/JsonServices.aspx?f=FunctionName
Header: ApiKey: <your key>
Content-Type: application/json

Functions

CreateContact            add a contact to a list
ChangeContactStatus      subscribe or unsubscribe a contact
SendSingleSmsMessage     one SMS, immediately
SendSingleEMailMessage   one email, immediately

Response

{ "ErrorCode": 0, "Result": "Call successful" }

Anything other than ErrorCode 0 is a rejection. 1 means the key or credentials were not accepted. 3 means the key was fine but the payload was missing something.

One field that is easy to miss

ReplyToEMail is required on SendSingleEMailMessage, even though it appears as an empty string in older documentation. Send it and the call succeeds; omit it and you get a null-reference error with code 3. We found this the hard way while building our own SMTP plugin.

Start integrating

Open a free account to get a key, and see the API overview for the SOAP interface and the IP allowlist.

Frequently asked questions

Which host do I call?

heb.mesereser.com. The login hosts are separate and do not serve the API.

How do I authenticate?

An ApiKey header on every request. There is no OAuth flow and no token exchange.

What does ErrorCode 3 mean?

The key was accepted but the payload was rejected. Usually a required field is missing.

Is there a sandbox?

No separate sandbox. Use a test list and a test contact on your real account.