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Is this a valid smtp? Does it work on port 25? Does it require a user name and password to authenticate? You may want to check with your IT as having a valid smtp server which doesn't require authentication or an email relay server would be the only way to trigger an event which sends you an email if a workflow fails.
As @MichalM mentioned, check that you have a valid SMTP relay address. Alternatively, you can use your relay's IP Address if that is easier to remember. Check with your IT to get the correct relay / IP address.