BUILD VERIFICATION TEST/SMOKE TEST are cursory tests that are helpful to determine the stability and testability of the build. These tests need to be run every time a build is deployed. The Build Verification test is preferable fast verification that centralize on core functionality.
Presume that the email app and the app you tested crashes very often whenever you archive near about 30-35 emails in succession (one after another). Afterwords, the developer asked to replicate the same issue, to do it manual this becomes the most tiresome task. Even after making some few attempts you replicate the issue and developer fixes it as well, you then has to take a conformation test to check that whether the issue is been resolved or not.

Automating the BVT's (Build Verification Test) and combine them to the continuous integration server will confirm that the modification made have not help to regressions. One thing to keep in mind while designing these tests is that the test should be short and should execute in few minutes.

Also consider the following while automating:

- Automation is a great option when we have to validate the same feature with large set of different inputs and data (Data-driven testing).
- Load and performance testing should be ideally automated where we test the systems ability to handle load by creating virtual users.