This article was developed to describe the process of enabling Simple Mail Transfer Protocol (SMTP) Settings for a client.
You may enter the SMTP credentials for your client under the My Settings page so that individual messages sent by you will go out through your server.
Regardless of who is your outgoing SMTP provider, you may be required to complete a few steps to ensure the functionality operates properly with our CRM. When you have entered the information requested in the image below, click the Test SMTP Settings to ensure your settings are correct.
Some security protocols include a Two-Factor Authentication (2FA) when logging into a new device, product, or location, even when 2FA is not enabled. An error message like the one below may result if more configuration is required.
This is for use on individual user profiles.
NOTE: It is strongly recommended to not use Google SMTP for senders to be used in e-marketing campaigns.
Troubleshooting Bad Credentials
If your SMTP credentials have been successfully authenticated, you will see the message below. 
If you received an error message like the example shown above after entering your credentials for outgoing mail settings and clicking Test SMTP Settings (see image below), the SMTP Provider may be preventing authentication as part of their security protocols.
To fix this, follow the steps below:
STEP 1: The first and most important step to troubleshoot your credentials is to double-check your username and password have been entered correctly. The following steps may require changes to your SMTP Provider configuration that will not work if your username and password are incorrect.
STEP 2: We recommend activating and using 2-step Verification even if you are not having issues with your SMTP. This is quickly being adopted and enforced on many platforms. For an example of more information regarding 2-step authentication, visit Google 2 Step Verification.
STEP 3: Generate an App Password, which is a multi-digit passcode that gives a less secure app or device permission to access your Account. App Passwords can only be used with accounts that have 2-Step Verification turned on. Basically, this acts similarly to how an API Key works. It is a dedicated password to be used in an outside system. In the case you are using 2FA with your SMTP Provider, you may need to use an App Password in your outgoing mail server settings. As an example, for information on generating an APP Password in Google, visit Sign in using app passwords.