In my experience of trying to calculate accurate click and open analytics, defining a user agent tells the software that they may want to exclude them and gives

In my experience of trying to calculate accurate click and open analytics, defining a user agent tells the software that they may want to exclude them and gives them an easy way to do it. Some bots use a user agent that looks like a normal browser, so you have to try to determine patterns based on timing of events, IP address, and other data. If the request has a custom user agent, all you have to do is exclude the datapoints that have that user agent on it. I personally always appreciate the bots that have custom user agents.