Me. Stat. tit. 14 § 153
The defendant in an action for libel may prove in mitigation of damages that the charge was made by mistake or through error or by inadvertence and that the defendant has in writing, within a reasonable time after the publication of the charge, retracted the charge and denied its truth as publicly and as fully as the defendant made the charge. The defendant may prove in mitigation of damages that the plaintiff failed to notify the defendant of the libel in a timely fashion and that the defendant was therefore unable to lessen damage to the plaintiff's reputation. The defendant may prove in mitigation of damages that the plaintiff has already recovered or has brought action for damages for, or has received or has agreed to receive compensation for, substantially the same libel. [RR 2009, c. 2, §30(COR).]
14 M.R.S. § 153