If you are experiencing issues with your email configuration, consider the following:
The first place to check would be your servlet engine logs which may provide clues if you are having problems communicating with your mail server.
If you go to your Unanet > About page, review what shows for the mail server and from & static addresses.
Is an address configured for the Default From Email Address? This can be managed with the Default From Email Address (unatime.email.default_from_address) property. This property will need to be set in order to send out any system initiated emails (i.e. scheduled email reminders).
Is an address configured for the Static From Email Address? This can be managed with the Static From Email Address (unanet.email.static_from_address) property. This may be necessary if you have end users with many different email address domains, and you find your email server is identifying them as spam. Using this property, you can define an email address having a domain that matches your email servers domain, and all email traffic coming from your Unanet instance will have this one From email address. Note that when using this property, the Reply To email address will be populated with the end user's email address (or the Default From Email Address if no user email available or if the message is a system initiated message vs an end user initiated message).
In your mail server, is relaying allowed in the SMTP setting from your Unanet webserver?
Is your virus protection configured to block e-mail messaging?