I would personally prefer using "\n". This just puts a line break in Linux or Android.
For example,
String str = "I am the first part of the info being emailed.\nI am the second part.\n\nI am the third part.";
Output
I am the first part of the info being emailed.
I am the second part.
I am the third part.
A more generalized way would be to use,
System.getProperty("line.separator")
For example,
String str = "I am the first part of the info being emailed." + System.getProperty("line.separator") + "I am the second part." + System.getProperty("line.separator") + System.getProperty("line.separator") + "I am the third part.";
brings the same output as above. Here, the static getProperty() method of the System class can be used to get the "line.seperator" for the particular OS.
But this is not necessary at all, as the OS here is fixed, that is, Android. So, calling a method every time is a heavy and unnecessary operation.
Moreover, this also increases your code length and makes it look kind of messy. A "\n" is sweet and simple.