How do I change an email password on my iPhone?

Some mail accounts, like Yahoo for example, don't let you change the password on your iPhone. It's been this way for some time, not just when iOS 18 was released. For an account you can't change the password on your iPhone, open the mail account on your computer and change the password there. Then when you open the account on your phone, you'll likely be prompted to then enter the new password.

"How do I change an email password on my iPhone?: This changed with the upgrade to IOS18. How do I change an email password on my phone?"

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Troubleshooting Logged Out of Mail After an Update:

A. Use a New App Password(If Applicable):

If you use an App Password, perhaps this has expired. So, remove the account, the add it back through use of a new App Password. For example, go here for gmail: Sign in with app password - Google Account Help

B. Report this to Apple:

So, do your Part: Provide Apple with feedback on this, letting them know about this issue.  Apple may not get back to you directly, but the more feedback they receive on this, the more they will know what is occurring, and what bug fixes to include in updates to come. Apple will know nothing of this, if you don't report it to them.

1. Go Here: Feedback - iPhone - Apple
2. Select: "Bug Report" for the "Feedback Type"
3. Comment: that this all began after installing an update. Include the URL of this thread
4. Proceed from there as necessary