what happens if there is no email specified? Are you sure that the the sbatch will not refuse to submit the job because the mail is empty?

In general if something is not used it is better to not specify it at all. look at Mario´s solution here https://github.com/vezzi/de_novo_scilife/blob/devel/sciLifeLab_utils/run_QC_analysis.py

there, if the email is not specified then two lines about the email are skipped.