Overview

Samsung devices running One UI offer two different Exchange ActiveSync (EAS) implementations when you add a mail account. The default Exchange option is Samsung's own built-in EAS client, while Microsoft Exchange is a separate implementation that becomes available once the Samsung Email app is installed.

When a Kerio Connect account is configured through the default Exchange option, calendar data can behave unpredictably: calendar colors change on their own, events appear at the wrong time, and some events never sync at all. This article explains why this happens and how to resolve it by configuring the account with the Microsoft Exchange option instead.

This behavior has been confirmed on a Samsung Fold running One UI 8.5 and on a Samsung Galaxy S26, and is likely to affect other Samsung devices running One UI 8.5 and later. It is a client-side behavior on the device and does not indicate a problem with the Kerio Connect server.

In This Article

• Symptoms
• Cause
• Resolution
• Expected Result
• Additional Information
• FAQ

Symptoms

On a Samsung device running One UI with a Kerio Connect account added through the default Exchange account type, you may see one or more of the following:

• Calendar colors change by themselves — the color assigned to a calendar account shifts without any user action.
• Events are time-shifted — appointments appear hours away from the time they were created in, and the correct time is still shown in Kerio Connect Client (webmail) and on other clients.
• Events fail to sync entirely, or sync only after a significant delay.

Email synchronization for the same account typically continues to work normally, which is why the issue is often first noticed only in the Calendar app.

Cause

Samsung One UI ships with two independent EAS client implementations:

• Exchange — Samsung's native EAS client. This is the account type offered by default when you add an account, and it does not require any additional app.
• Microsoft Exchange — a separate EAS implementation that becomes available only after the Samsung Email app is installed.

The default Exchange client has known problems with calendar color consistency, event time accuracy, and sync reliability when connected to an EAS server. These problems do not occur when the same account is configured with the Microsoft Exchange client, which handles the same calendar data correctly.

Because the server sends identical data to both clients, the difference is entirely in how each client interprets and stores it on the device.

Resolution

Reconfigure the Kerio Connect account on the device using the Microsoft Exchange account type.

Before you begin, collect the following account details:

• Your Kerio Connect email address
• Your Kerio Connect server name or URL
• Your domain and username, in domain\username format
• Your account password

Step-by-step Instructions

• Install the Samsung Email app from the Galaxy Store or Google Play Store (if not already installed)
• On your Samsung device, go to Settings → Accounts and backup → Manage accounts → Add account
• Instead of selecting "Exchange", select "Other"
• Go to Manual settings
• Select "Microsoft Exchange" as the account type
• Enter your Kerio Connect server details:
  • Email address: your Kerio Connect email
  • Server: your Kerio Connect server URL
  • Domain\Username: your domain and username
  • Password: your account password
• Complete the setup and verify that calendar sync is working

Expected Result

After the account is configured with the Microsoft Exchange account type:

• Calendar colors stay as assigned and no longer change on their own.
• Events display at their correct times, with no shifting.
• Calendar synchronization runs reliably, with no missing events.

Additional Information

Both account types use the same Exchange ActiveSync protocol against the same Kerio Connect server, so no server-side configuration change is needed and no other clients are affected by this switch.

For general EAS setup guidance on Android, see Configuring Exchange ActiveSync Accounts on Android Devices. Note that its screenshots reflect an older Android release and it uses the default Exchange option; on Samsung One UI devices, follow the steps in this article instead.

An earlier article, Some Calendar Items Are Not Syncing to the Samsung Device, describes a different Samsung calendar sync problem seen on Android 9 and 10 and recommends the opposite account type. That guidance applies to those older releases; for One UI 8.5 and later, use the Microsoft Exchange option described here.

If calendar problems persist after switching account types — particularly if email also stops syncing — the mailbox may have an inconsistent ActiveSync state on the server. See Resolving Kerio Connect Email Synchronization Issues on Mobile Devices.

FAQ

Q1: Do I have to use the Samsung Email app after switching to the Microsoft Exchange account type?
No. The Samsung Email app only needs to be installed so that the Microsoft Exchange account type appears during setup. Once the account is added, your calendar continues to appear in the Samsung Calendar app as before, and you can keep using whichever mail app you prefer.

Q2: Will I lose any calendar events when I remove the old account and add the new one?
No. All calendar data lives on the Kerio Connect server, and removing an account only clears the copy cached on the device. The new account downloads the data again. If you created events on the device while it was offline and they never reached the server, confirm they are visible in Kerio Connect Client before removing the old account.

Q3: Does this issue mean something is wrong with my Kerio Connect server?
No. The server sends the same data to both Samsung EAS clients, and the same account syncs correctly through the Microsoft Exchange client and through other devices. The inconsistent colors, shifted times, and missed events come from how Samsung's default Exchange client processes the data on the device.