Very simple solution:
Contacts.php line 137 find line...<td colspan="2" class="contact_submit"><input type="submit" name="do_submit" value="<?= _t('_Submit') ?>" disabled="disabled"/>

Change to....<td colspan="2" class="contact_submit"><input type="submit" name="do_submit" value="<?= _t('_Submit') ?>" disable="disabled"/>

eliminates the see more manual typing of email address.