You should endorse checks payable to your mother or to her estate:|
For deposit only
Estate of [Your mother's name]
By [Your signature], Executor
Presumably, the checks you write on the estate account are pre-printed to indicate they are issued by the estate of [your mother's name]. You should sign these checks simply with your own signature, followed by "Executor" or "Exec."
Published on BankingQuestions.com 4/30/09