Theres a new Priority Notifications feature in iOS 18.4 to ensure important messages and alerts get prominent Lock Screen placement. But a different feature entirely was added in a recent iOS updateCritical Messagesthat enables apps to send your iPhone highly important messages via SMS. Heres how it works.New messaging feature involves very specific parameters to prevent spamWith an iPhone update over the last few months, Apple has given developers a new capability to send SMS alerts to users. But its only intended for very specific and critical situations.Heres the description from Apples documentation:The Critical Messaging API provides a way for apps to deliver critical messages to a set of phone numbers. This can serve a number of purposes. For example, if an enterprise wants to receive check-ins from employees working in hazardous or rural environments, being able to automatically message a corporate check-in point may help check the safety of those employees without disrupting their work, or if the employee is unable to access or unlock their iPhone.Since this feature could potentially be abused by some developers, there are very specific conditions Apple has set to ensure that Critical Messages doesnt lead to spamming users with advertising or other unwanted alerts.For example, Apple specifies: You may not use the Critical Messaging API for sending unsolicited messages or for phishing or spamming, including but not limited to engaging in any types of activities that violate anti-spamming laws and regulations, or that are otherwise improper, inappropriate, or illegal.From a users standpoint, its unlikely youll receive Critical Messages often. Similar to the existing Critical-level notifications, theyre expected to be rarely deployed only for very important, time-sensitive notices.If you do find yourself receiving Critical Messages you dont want, theres an opt-out option in iOS that can be applied to individual apps. To opt out, simply open your iPhones Settings app, then go to Privacy & Security Critical Messages. Any apps that have requested permission to send these types of messages will appear here and can be disabled.What do you think of the iPhones Critical Messages feature? Let us know in the comments.Best iPhone accessoriesAdd 9to5Mac to your Google News feed. FTC: We use income earning auto affiliate links. More.Youre reading 9to5Mac experts who break news about Apple and its surrounding ecosystem, day after day. Be sure to check out our homepage for all the latest news, and follow 9to5Mac on Twitter, Facebook, and LinkedIn to stay in the loop. Dont know where to start? Check out our exclusive stories, reviews, how-tos, and subscribe to our YouTube channel