springboot maven项目，为什么build成功，build path也没错误，project-->clean 也没用，项目上面还是有个红x呢？

看错误信息有提示：

Description Resource Path Location Type
Project configuration is not up-to-date with pom.xml. Select: Maven->Update Project... from the project context menu or use Quick Fix. sendemail line 1 Maven Configuration Problem

解决办法：右键项目 maven-->update project 后就可以了