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Host - It allows you to choose a provider (added in the Notification Providers tab).
Email address - email Email address from which the message messages will be sent.
Username - Enter the address username.
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TLS - When you tick the TLS checkbox, the communication with the email server is encrypted with TLS. if If not , checked - it is encrypted with SSL by default.
Test connection - by By clicking this button you can test the connection with your mail server and check if the notifications will be sent properly.