Mail not working on iPhone after iOS 18 Update

I’d get the server to TLSv1.2 and with forward security configured minimally, and test again.

IMAP (read, receive) and ESMTP (send) are separate network services, so check both.

There are various ways to check the TLS and cipher offers by a server, and curl and testssl among those,:

https://stackoverflow.com/questions/40557031/command-prompt-to-check-tls-version-required-by-a-host

Also check the IMAP and ESMTP server logs for any failure-relevant details that might be included there.

Hello, somehow, self-signed certificates don't work anymore (even though they could be trusted before and most likely adhere to the requirements).

I was able to provide MDM payload with a Step-CA root certificate, its intermediate certificate and the signed certificate of the mailserver - it seems to be important that the chain of trust be completely working, including working DNS and alt name of the host. With iOS18.0.1, i have my mail back working.

If there are other bugs (like Prefixes on IMAP paths) i don't know, but i did not experience them and by looking in the SMTP/IMAP server logs, i was confirmed enough that TLS did not work.

Finally resolved with help from my email provider (names.co.uk). Posting in case this helps others.

I had always used mail server addresses as imap.(my domain) and smtp.(my domain). I had to change server addresses to the umbrella mail host (Unified Layers) who host for quite a number of different providers: us2.imap.mailhostbox.com and us2.smtp.mailhostbox.com with my username and password for login. This has resolved the problem on my iPhone.

MacBook still works using my domain name mail server addresses, for now at least 😁

One other thing, I don’t like the way Mail accounts are now within the Apps menu 🤨

FIXED

This problem is with IMAP folders that have special charecter,

I had in mine "á" in one of the folders , I renamed the folder and just used non special chars.

Fixed the problem.

Others here might have SSL Cert problems, but that is a different problem.

I have checkd this on Server side and Client side , tested back and forward.

IMAPS accounts with no folders sync fine in IOS 18, thouse that have special chars will give you this error.

Also this error is very confusing since it points users in the wrong direction.

I was able to fix my issue.

When you delete the mail account, make sure to restart your iPhone. After restart, add mail account and enter info and once it asked me to trust the security certificate, it worked. (previously I didn't restart after deleting and trusting the security certificate didn't do anything).

Hi All,

After much frustration, this problem was resolved for me by adding a / (forward slash) in the IMAP Path Prefix field.

The Path Prefix field can be found under Settings>Apps>Mail>Mail Accounts>[your IMAP account]>Account Settings>Advanced ... then in the Incoming Settings section you will find IMAP Path Prefix (it may have a slightly grey / after it. Type / and the / will turn white. Then back out of that menu and press Done. Close settings and your mail app. Open your mail app and see if it now works.

Note: some people add INBOX to the path prefix, but at least in my case this prevented the other folders from syncing as they are in the root of the IMPA server.

Hope it works for others - this was SO frustrating!

Cheers!

OK, also here, IMAP stopped working on my Iphone after upgrade to IOS 18.

Ipad remained working on IOS 17.

Installing another mail client on the Iphone fixed the issue, clearly Apple changed something in their Mail app.

Had contact with customer support a few times, but what strikes me is that they are not aware of anything that changed!

I also used self signed certificate for years. After playing around for a while I decided to replace them with Let's Encrypt certificated.

Then it instantly started to work again and the error messages on the server side were gone, indicating the client had difficulties with the self-signed certificate.

So Apple, please fix the self-signed certificate support again and, AT LEAST, inform the public and your helpdesk people that something has changed so people like use are/can be informed.

Lacking information and transparency here is killing!

This is how I fixed my issue. My addy was ...@gmail.com

Go to Settings … scroll all the way down to Apps …

 - Go specifically to: Settings>Apps>Mail>Mail Accounts>Select your mail account>Account Settings>Advanced

 - In the group “INCOMING SETTINGS,” the second line should read: "IMAP Path Prefix /“

 - You may notice the forward slash “/“ is grayed out and not the same contrast as the three words prior.

 - Type a forward backslash “/“ next to the grayed out /

 - Now delete the grayed out forward backslash “/." Just tap to the left of the new backslash you typed and backspace to delete the grayed out backslash.

 - Finally, perform a hard reboot of your phone in the following order: 1. Press and release the left outside volume up button. 2. Press and release the left outside volume down button. 3. Press and HOLD the right outside power button UNTIL the phone shuts down, restarts AND you see the Apple. 

This fixed it for me.

THIS FIXED IT FOR ME!

I tried every possible fix and nothing helped. Then I came across your comment. I am from Germany and we have letters in our alphabet that are not included in ASCII. For example ä,ü,ö. I changed all the folder names in my webmail client that had these letters in them to something else. It immediately worked. I also send a couple of these mail and the immediately push in.

I hope this helps someone.

https://en.wikipedia.org/wiki/ASCII

Go to Character set so see what's "allowed".

Thanks again for the idea - whoever had it!

Hey everyone,

This is a bug in the iOS Mail app.

If the IMAP server returns an INTERNALDATE in this format:

👉 "12 Aug 2024 12:04:03 +0800"

the Mail app fails to connect to the server.

However, if the IMAP server returns the INTERNALDATE in this format:

👉 "12-Aug-2024 12:04:03 +0800"

the issue magically disappears, and everything works fine.

So, what’s next? Either Apple fixes this bug, or mail server software vendors will have to adjust their IMAP response specifically for the iOS Mail app.

For example, the mail server software I use (EvoMailServer) has an option in the user account settings to change the IMAP compatibility mode, and enabling it resolved the issue.

Why isn’t this a bug in the mail server?

Well, if the Mail app couldn't read the date properly, it should report an error related to the date format. But instead, it throws an error message about a completely unrelated issue. That’s why this is clearly a bug in the iOS Mail app, not the mail server.

For those who manage their own mail server using self signed certificates there are a number of options to move to LetsEncrypt certificates which fixes the problem. This is a high level recipe for Amazon Linux 2.

Follow this :

https://gist.github.com/mrothNET/cb6f313e9cbe896f3e0fdec80ad2f3fa

Points to note - I also run https on this server to I had to stop the service, get the certificate and then restart the service.

I didn’t do the bit for cli.ini for auto-renewal, but read this article instead:

https://stackoverflow.com/questions/42300579/letsencrypt-certbot-multiple-renew-hooks

I followed the answer for Centos/Amazon Linux.

I had to enable the certbot-renew.timer service

I then edited /etc/sysconfig/certbot and added a PRE_HOOK to stop httpd, POST_HOOK to start httpd and a DEPLOY_HOOK to restart postfix and dovecote (similar to what was posted in the first article for cli.ini) Don’t forget to keep or add the command line switches (eg. —pre-hook) that are in the examples shown in the file

Obviously I don’t know if the renew will work as it takes a bit of time, but after the restarting of dovecot and postfix in the first article, mail started working again.

TLS 1.1 is obsolete and has been deprecated.

You need to get your mail server up to speed.

It needs to be using TLS 1.2 or higher.

Ok. I found the problem on my side!

The 2 accounts that where not working where using IMAP folders with some specials characters in their name.

No problem with iOS 17 and many years prior that. And no problem with other mail client ... but they makes the connection fails with iOS18.

After I renamed thoses folder (and changed all my setting on all my different clients...) ... it works again!

After working with a rep, I was able to resolve. Here is what I did:

Deleted the mail app

Reinstalled from the app store

After that, went to Settings > Apps > Mail > Accounts 

Enabled mail for all accounts 

Restarted the phone.

Still not working after that, so then I deleted the email account and re-added it. Mail then began working.

NickAleshgo wrote:

• Here

TLS 1.0 and TLS 1.1 are being deprecated due to security concerns: 

Security vulnerabilities

• TLS 1.0 and TLS 1.1 are vulnerable to a number of attacks, including POODLE, BEAST, CRIME, FREAK, and LOGJAM. These attacks can compromise encrypted communications and expose valuable data. 

• Compliance requirements

• Many organizations, including government agencies, must meet compliance requirements that mandate the use of TLS 1.2 or higher. 

• Evolving standards

• Internet standards and regulatory bodies are evolving to provide improved security. 

• Here are some details about the deprecation of TLS 1.0 and TLS 1.1: 

Windows

• TLS 1.0 and TLS 1.1 will be disabled by default in Windows 11 Insiders Preview and Windows Server Insiders Preview releases in 2024. This change applies to both client and server devices. 

• Azure

• Azure will remove support for TLS 1.0 and TLS 1.1 for new and existing storage accounts by October 31, 2024. 

• Internet Engineering Task Force (IETF)

• The IETF officially deprecated TLS 1.0 and TLS 1.1 in March 2021. The IETF recommends that companies, government agencies, and software developers use TLS 1.2 and TLS 1.3. 

While that is good info for people, This imap failure on the mail app on iOS and iPadOS 18 is happening on servers that use TLS 1.2 and 1.3