With the introduction of inline dynamic content, it is easy to include dynamic content in the email body when using the Contact Form module.
For each Contact Form module where you want to include the Post/Page's title in the Email body, open its settings by clicking on the Gear icon or by clicking on the module itself.
In the Content tab, click on the Email option group.
In the Message Pattern field, add any pattern that suits your use case, for example:
Name: %%Name%%
Email: %%Email%%
%%Message%%
Click on the Dynamic Content icon
. 
Choose the Post/Archive Title option.
Note:
Make sure you use the correct field IDs when composing the Message Pattern. The %%Name%%, %%Email%%, and %%Message%% represent the Name, Email, and Message default field IDs.