For testing email advisable to use a special kind of testing - Split testing (or A/B testing). UniSender is a service that allows you to automate the A/B test and reduce the time of result analysis to a minimum. UniSender has the option to choose a free plan for 1 year. You can send up 1500 emails per month with no more than 100 subscribers.
Speed and reliability testing (load / stress / performance testing). This test helps to check a behaviour of websites (or its parts) at the same time with an influx of a lot of users. Poor performance (speed) - this is the main issue of many Internet projects. You can build really cool useful site, but low performance could decreased all your achievements.
In many companies, unfortunately, underestimate the influence of the static test on the quality of the final product. At first, let's start with terms to understand differences between static and dynamic testing. In contrast to dynamic testing, static testing finds causes of defects and help to prevent future failures. It often has a goal to educate team and new team members. Static testing is done before the dynamic test and accordingly, errors found at this stage costing us less.