AceProject has e-mail notifications that are generated when a user performs an action (like, for instance, assigning or updating a task) and others that are not the result of a connected user’s action (for instance, the Task Reminder e-mail notification). In the latter case, the FROM address of the e-mail notification will be the one specified in the “Default E-mail” field.
Please refer to this help topic for information on troubleshooting e-mail notification issues.