Couldn't Store the SMTP Password

Question

In SharePoint Central Administrator 2019, I'm attempting to configure the outgoing mail, but I keep getting the following problem when saving the settings: couldn't store the SMTP password. The application credential key wasn't found on the local server or there was an encryption error.

As seen in the picture below:

P.S: The username and password are definitely correct.

Answer 1

Set Application credential key in SharePoint 2019

To solve this issue "couldn't store the SMTP password. The application credential key wasn't found on the local server or there was an encryption error.", you have to set the application credential key, by running the following command on each SharePoint server:

Set Application Credential Key PowerShell Example:

$key = ConvertTo-SecureString -AsPlainText -Force "The "application credential key" # is the password to be used to encrypt and decrypt the SMTP password.
Set-SPApplicationCredentialKey $key

Note: Repeat the command on each additional SharePoint server in the farm, using the same application credential key.

Remove Application credential key in SharePoint 2019

If you want to remove the application credential key from the local server, use the Remove-SPApplicationCredentialKey cmdlet as below:

Remove-SPApplicationCredentialKey -Confirm:$false