Error when synching mail with Mailbox.org

I recently switched from Proton Mail to Mailbox.org and now I’m in the process of moving my emails. I exported all of them from Proton and imported them to the configured account of Mailbox in eM Client. Some uploaded fine but now I always get a red exclamation mark next to the account. Restarting the app or hitting refresh just leads back to the exclamation mark. I can’t really figure out what the error log is telling me… If someone could have a look and point me in the right direction on how to fix this, that would be awesome.

eM Client 10.1.4600+b91743360a (Windows Store)
22:23:23 Mailbox [IMAP] MailClient.Accounts.ConnectionException: Failed opening connection to server.
—> System.IO.IOException: No server response within 30 second timeout.
at MailClient.Imap.Base.Connection.ConnectAsync(Func2 getStream, CancellationToken cancellationToken) at MailClient.Protocols.Imap.ConnectionPoolEntry.ConnectInternalAsync(CancellationToken cancellationToken) --- End of inner exception stack trace --- at MailClient.Protocols.Imap.ConnectionPoolEntry.ConnectInternalAsync(CancellationToken cancellationToken) at MailClient.Protocols.Imap.ConnectionPoolEntry.ConnectInternalAsync(CancellationToken cancellationToken) at MailClient.Protocols.Imap.ConnectionPool.AcquireConnectionAsync(Folder mailFolder, Boolean noSelect) at MailClient.Protocols.Imap.ConnectionContext.CreateContextAsync(ImapAccount account) at MailClient.Protocols.Imap.ImapFolderSynchronizer.CreateFolderAsync(Folder folder, CancellationToken cancellationToken) at MailClient.Protocols.Imap.ImapFolderSynchronizer.Upload(FolderUploadContext uploadContext, Folder folder, CancellationToken cancellationToken) at MailClient.Protocols.Common.FolderSynchronizer.<>c__DisplayClass20_0.<EnqueueUpload>b__0(WorkerStatus status, CancellationToken cancellationToken) at MailClient.Protocols.Imap.ImapActionCommand.<>c__DisplayClass11_0.<.ctor>b__0(WorkerStatus ws, CancellationToken ct) at MailClient.Protocols.Imap.ImapActionCommand.ExecuteInternalSync(WorkerStatus status) at MailClient.Protocols.Imap.ImapActionCommand.Execute(WorkerStatus status) at MailClient.Commands.Command.Process(WorkerStatus status) AccountId = 0820d0d9-0a51-438e-98c8-e3eadd024315 AccountName = Mailbox IMAP_SERVER_TYPE = Dovecot RunInPlace = False EnqueuedStackTrace = at MailClient.Protocols.Common.FolderSynchronizer.EnqueueUpload(Folder folder) at MailClient.Protocols.Common.FolderSynchronizer.GoOnlinePre() at MailClient.Protocols.Imap.ImapFolderSynchronizer.GoOnlinePre() at MailClient.Protocols.Imap.ImapAccount.GoOnlineInt() at MailClient.Protocols.Common.AccountBase.ChangeOnlineState(Boolean online, OfflineReason offlineReason) at MailClient.Protocols.Common.AccountBase.GoOnline() at MailClient.Accounts.AccountList.<>c__DisplayClass24_0.<SetOnlineState>b__1(IAccount account) at System.Threading.Tasks.Parallel.<>c__DisplayClass43_02.b__1(IEnumerator& partitionState, Int64 timeout, Boolean& replicationDelegateYieldedBeforeCompletion)
at System.Threading.Tasks.TaskReplicator.Replica1.ExecuteAction(Boolean& yieldedBeforeCompletion) at System.Threading.Tasks.TaskReplicator.Replica.Execute() at System.Threading.Tasks.TaskReplicator.Replica.<>c.<.ctor>b__4_0(Object s) at System.Threading.Tasks.Task.InnerInvoke() at System.Threading.Tasks.Task.<>c.<.cctor>b__281_0(Object obj) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread) at System.Threading.Tasks.Task.ExecuteEntryUnsafe(Thread threadPoolThread) at System.Threading.Tasks.ThreadPoolTaskScheduler.TryExecuteTaskInline(Task task, Boolean taskWasPreviouslyQueued) at System.Threading.Tasks.TaskScheduler.TryRunInline(Task task, Boolean taskWasPreviouslyQueued) at System.Threading.Tasks.Task.InternalRunSynchronously(TaskScheduler scheduler, Boolean waitForCompletion) at System.Threading.Tasks.Task.RunSynchronously(TaskScheduler scheduler) at System.Threading.Tasks.TaskReplicator.Run[TState](ReplicatableUserAction1 action, ParallelOptions options, Boolean stopOnFirstFailure)
at System.Threading.Tasks.Parallel.PartitionerForEachWorker[TSource,TLocal](Partitioner1 source, ParallelOptions parallelOptions, Action1 simpleBody, Action2 bodyWithState, Action3 bodyWithStateAndIndex, Func4 bodyWithStateAndLocal, Func5 bodyWithEverything, Func1 localInit, Action1 localFinally)
at System.Threading.Tasks.Parallel.ForEachWorker[TSource,TLocal](IEnumerable1 source, ParallelOptions parallelOptions, Action1 body, Action2 bodyWithState, Action3 bodyWithStateAndIndex, Func4 bodyWithStateAndLocal, Func5 bodyWithEverything, Func1 localInit, Action1 localFinally)
at System.Threading.Tasks.Parallel.ForEach[TSource](IEnumerable1 source, Action1 body)
at MailClient.Accounts.AccountList.SetOnlineState(Boolean online, OfflineReason offlineReason, IComparer1 comparer) at MailClient.Accounts.BindingAccountBase.GoOnline() at MailClient.Accounts.AccountList.<>c__DisplayClass24_0.<SetOnlineState>b__1(IAccount account) at System.Threading.Tasks.Parallel.<>c__DisplayClass43_02.b__1(IEnumerator& partitionState, Int64 timeout, Boolean& replicationDelegateYieldedBeforeCompletion)
at System.Threading.Tasks.TaskReplicator.Replica1.ExecuteAction(Boolean& yieldedBeforeCompletion) at System.Threading.Tasks.TaskReplicator.Replica.Execute() at System.Threading.Tasks.TaskReplicator.Replica.<>c.<.ctor>b__4_0(Object s) at System.Threading.Tasks.Task.InnerInvoke() at System.Threading.Tasks.Task.<>c.<.cctor>b__281_0(Object obj) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread) at System.Threading.Tasks.Task.ExecuteEntryUnsafe(Thread threadPoolThread) at System.Threading.Tasks.ThreadPoolTaskScheduler.TryExecuteTaskInline(Task task, Boolean taskWasPreviouslyQueued) at System.Threading.Tasks.TaskScheduler.TryRunInline(Task task, Boolean taskWasPreviouslyQueued) at System.Threading.Tasks.Task.InternalRunSynchronously(TaskScheduler scheduler, Boolean waitForCompletion) at System.Threading.Tasks.Task.RunSynchronously(TaskScheduler scheduler) at System.Threading.Tasks.TaskReplicator.Run[TState](ReplicatableUserAction1 action, ParallelOptions options, Boolean stopOnFirstFailure)
at System.Threading.Tasks.Parallel.PartitionerForEachWorker[TSource,TLocal](Partitioner1 source, ParallelOptions parallelOptions, Action1 simpleBody, Action2 bodyWithState, Action3 bodyWithStateAndIndex, Func4 bodyWithStateAndLocal, Func5 bodyWithEverything, Func1 localInit, Action1 localFinally)
at System.Threading.Tasks.Parallel.ForEachWorker[TSource,TLocal](IEnumerable1 source, ParallelOptions parallelOptions, Action1 body, Action2 bodyWithState, Action3 bodyWithStateAndIndex, Func4 bodyWithStateAndLocal, Func5 bodyWithEverything, Func1 localInit, Action1 localFinally)
at System.Threading.Tasks.Parallel.ForEach[TSource](IEnumerable1 source, Action1 body)
at MailClient.Accounts.AccountList.SetOnlineState(Boolean online, OfflineReason offlineReason, IComparer1 comparer) at MailClient.Accounts.AccountManager.SetOnlineState(Boolean toOnline, OfflineReason offlineReason) at MailClient.Accounts.DesktopAccountManager.SetOnlineState(Boolean toOnline, OfflineReason offlineReason) at MailClient.Accounts.AccountManager.set_ForcedOffline(Boolean value) at MailClient.Licensing.MicrosoftStore.MicrosoftStoreLicenseSource.<>c__DisplayClass23_0.<LicenseRetrieved>b__4() at MailClient.UI.LongOperationService.<>c__DisplayClass12_0.<InitOperation>b__0(CancellationToken ct) at MailClient.UI.LongOperationService.<>c__DisplayClass15_01.<b__0>d.MoveNext()
at System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[TStateMachine](TStateMachine& stateMachine)
at MailClient.UI.LongOperationService.<>c__DisplayClass15_01.<InitOperation>b__0() at System.Threading.Tasks.Task1.InnerInvoke()
at System.Threading.Tasks.Task.<>c.<.cctor>b__281_0(Object obj)
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
at System.Threading.Tasks.Task.ExecuteEntryUnsafe(Thread threadPoolThread)
at System.Threading.Tasks.Task.ExecuteFromThreadPool(Thread threadPoolThread)
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()
at System.Threading.Thread.StartCallback()
GUIStatus_Exception_Reported = True
22:23:23 Mailbox [IMAP] System.Threading.Tasks.TaskCanceledException: A task was canceled.
at MailClient.Protocols.Imap.ImapAccount.SynchronizeIntAsync(Boolean forced)
at MailClient.Protocols.Common.SynchronizableMailAccount.<>c__DisplayClass22_0.<b__0>d.MoveNext()
GUIStatus_Exception_Reported = True

I solved it by switching to Thunderbird. Thanks.