If you receive the error message “The SMTP information you have provided is incorrect” or anything similar, while trying to activate the SMTP feature on your web form, check if your credentials are correct.
Do you use Gmail? If the issue persists, it could mean that Google blocks the connection. This can be avoided by going to the security settings of your Google account and clicking on Allow less secure apps. Next, tick Turn on, Also. make sure that you do not have the Google 2-Step Verification option enabled.