When length of subject in private message is too long, it goes beyond the page

Preconditions: User1, User2 accounts are created
1. Login to forum as User1
2. Click on "Messages"in top menu
3. Click on "Compose"
4. Enter User2 name in "To" field
5. Enter text string of 120 symbols into "Subject"field
6. Press "Send" button
7. Login to forum as User2
8. Verify incoming message from User1

AR: Subject of 120 symbols goes beyond the page(see an attach).
ER: The first symbols of subject are shown, the rest is hidden