[CLEANUP] #4283 More cleanup of the mailer classes.

Change-Id: I1a046c90f94b6c43c3a3ddf098b3d7a0b19fb7d2
Reviewed-on: http://review.typo3.org/32478
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>