The relationship between Employee and e-mail is poorly implemented here.
There is low cohesion.
Note:
Low cohesion is associated with undesirable traits such as being difficult to maintain, difficult to
test, difficult to reuse, and even difficult to understand.
Cohesion is decreased if:
The functionalities embedded in a class, accessed through its methods, have little in common.
Methods carry out many varied activities, often using coarsely-grained or unrelated sets of data. Disadvantages of low cohesion (or"weak cohesion") are:
Increased difficulty in understanding modules. Increased difficulty in maintaining a system, because logical changes in the domain affect multiple modules, and because changes in one module require changes in related modules. Increased difficulty in reusing a module because most applications won't need the random set of operations provided by a module. Reference:Cohesion (computer science)