> ## Documentation Index
> Fetch the complete documentation index at: https://moengage.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Why Does an SMTP Service Disconnect Error Occur When Testing an Email Campaign?

> Resolve the SMTP service disconnected error when testing MoEngage email campaigns, typically caused by incorrect email connector credentials.

## Problem

While testing an Email campaign, the following error message occurs:

SMTP service disconnected

<img alt="000.png" src="https://mintcdn.com/moengage/S5VM4C7aiU6sct6c/images/moengage_070322.png?fit=max&auto=format&n=S5VM4C7aiU6sct6c&q=85&s=80a30552d33dfc21f7f239b27d47e42d" width="988" height="536" data-path="images/moengage_070322.png" />

## Cause

Typically, this error occurs due to incorrect credentials.

## Solution

* The error originates from the SMTP connector.
* Verify whether MoEngage manages the Email connector (SendGrid) or if another provider is used.