Pros
If you can handle the fire, there is growth potential at this company. There has been a lot of hiring and new positions open. Promotions tend to be infomral and not subject to a rigorous process.
Cons
The company claims to be "for developers", but most of the leaders in the company are incapable of using the product. Even worse, occasionally leaders who aren't technical speak as if they are an authority on what technical users want. A company the size of Mailgun frequently takes on the identity of the leader of the company. This is rarely endearing and at Mailgun this is no exception. Some of the leaders are unnecessarily vulgar and publicly embarrass and humiliate others. You must have thick skin to work here. Expect the bar to constantly change. With elevated job titles, some executives are struggling with keeping their ego under control. It is the rule, not the exception, to accommodate an executive. Expect some of them to be routinely late and have no respect for the impact on others. Ironically, people are fired symbolically, such as for missing a meeting. The stereotypical "sales culture" is pervasive at Mailgun. Those who are loud and obnoxious are elevated.