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New Contributor

Unable to get iPhone mail via WiFi on FortiGate 100E

We have several locations running Fortinet equipment and we can't get to our on-prem Exchange server when using WiFi from only one of the locations.


Main office has a Fortigate 200.  Outlaying offices both have Fortigate 100E.  A site-to-site tunnel connects everything.  When we're at the main office and on WiFi, any iPhone will connect to email using the Mail app perfectly.  When we go to office A with the same iPhone, everything works fine.  When we go to Office B (running FortiOS 6.2.11) with the same iPhone, we can't reach the Exchange server (via mail app or owa address).  We're able to ping the server just fine.  If we use an Android or a laptop in that same office, there is no issue - it is ONLY the iPhone.


Sniffer logs show the Client Hello going from the iPhone to the Exchange server.  Logs on the HQ 200 show that the Server Hello gets sent to the 100E but then the connection times out (maybe due to using TLS 1.0 somehow?).


Again - the same iPhone will work in our other locations just fine.  It's only this ONE location that is having issues.


Has anyone experienced something similar?  Does anyone know of any magic setting in the 100E that may need to be changed?  Is there a way to use the 100E to find out what happens to the traffic?




Thank you SO MUCH for your help.  I change the MTU to 1380 and it worked, although I had to use commands that differed from yours since they didn't seem to have effect:


config system interface
 set mtu 1380

  That was after I was in the interface and did set mtu-override enable and tried the tcp-mss 1380 but that didn't work.  Running set mtu 1380 did though.


Is the way I implemented the change going to work long term without affecting other traffic? 


Hey there yeah setting MTU is a good idea too. However, not all connections/devices will recognize the lower MTU and might still send packets that are too big. If it's working for you, great.


I would suggest a combo play: set MSS to 1380 and MTU to 1420. See how that works. Having only MTU set might cause delays/timeouts for some traffic still.


Is the WAN connection a PPPoE or similar connection with extra overhead? If so you  might want to manuall set the MTU on the WAN link as well...

New Contributor

I searched on every forum on internet and eventually end up fixing this by encountering the message "This message has not been downloaded from the server" in the iPhone Mail app, there are several potential solutions you can try to resolve the issue. Here are some steps to troubleshoot:-

1. Check Internet Connection:-
  -Ensure that your iPhone has a stable and active internet connection, either through Wi-Fi or               cellular  data. If the connection is weak or unstable, it might prevent the mail from being                       downloaded.

2. Refresh or Reload the Mail App:-
  -Open the Mail app, navigate to the mailbox with the problematic message, and try pulling down on     the screen to refresh the mailbox. This action often triggers the app to re-download messages.

3. Restart the Mail App:-
  -Close the Mail app and then reopen it. To close an app on iPhone with Face ID, swipe up from the     bottom and hold to access the app switcher. For iPhones with a Home button, double-click the             Home button and swipe up on the Mail app.

4. Restart Your iPhone:-
  -A simple restart of your iPhone can resolve many software-related issues. Turn off your iPhone,         wait a few seconds, and then turn it back on.

5. Check Mail Settings:-
  -Make sure your email account settings are correctly configured. Go to Settings > Mail > Accounts,       select your email account, and verify that the incoming mail server settings are accurate.

6. Delete and Re-Add Email Account:-
  -Remove the problematic email account from your iPhone and then add it again. Go to Settings >         Mail > Accounts, select the email account, and choose "Delete Account." Afterward, add the                account again using the "Add Account" option.

By following these steps, you should be able to troubleshoot and resolve the issue with messages not being downloaded from the server in the iPhone Mail app. For more details follow instruction.

New Contributor

I looked for this on various websites including youtube and solved it using to get a "Cannot Get Mail" error on your iPhone. Here are some steps you can try to fix it:-

1. Internet Connection:- Make sure your iPhone has a strong and stable internet connection. Try using a different Wi-Fi network or switch to cellular data to see if that resolves the issue.

2. Email Password:- Double-check that you're entering the correct email address and password for your account.

3. Mail App Restart:- Sometimes a simple restart of the Mail app can fix the issue. Close the Mail app completely by swiping up on it in the app switcher (double-tap home button and swipe up on previews). Then, relaunch the Mail app.

4. Mail Fetch Settings:- Go to Settings > Mail > Accounts and tap on the specific email account having issues. Check the Fetch New Data settings. In some cases, iPhones only fetch new emails when on Wi-Fi or at specific intervals. You might want to adjust these settings to "Push" for more frequent updates.

5. Remove and Re-add Email Account:- If none of the above solutions work, try removing and re-adding your email account in the Mail app. Go to Settings > Mail > Accounts, tap on your email account, and select "Delete Account". Then, follow the steps to re-add your email account.

6. Contact Email Provider:- In some cases, the issue might be related to your email service provider. Check their status page for any reported outages or contact their customer support for further assistance. More effective instruction below.


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