problems manging many mails and folders

I have a lot of folders, and a lot of mails. When I jump from one folder to another (looking for a mail manually) the em client shuts down. It has happened many times.

This is the error detail:
The following error has occurred:
System.OutOfMemoryException: Se produjo una excepción de tipo ‘System.OutOfMemoryException’.
en System.IO.MemoryStream.set_Capacity(Int32 value)
en System.IO.MemoryStream.EnsureCapacity(Int32 value)
en System.IO.MemoryStream.Write(Byte[] buffer, Int32 offset, Int32 count)
en MailClient.Pop3.Pop3ReceiveCommand.ReadMail(Int64 messageSize, Int64& downloadedBytes, Int64 totalBytes, WorkerStatus status)
en MailClient.Pop3.Pop3ReceiveCommand.Execute(WorkerStatus status)
en MailClient.Commands.Command.Process(WorkerStatus status)
en MailClient.Commands.SynchronizationQueue.ThreadWorker(Object threadData)
en System.Threading.ThreadHelper.ThreadStart_Context(Object state)
en System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
en System.Threading.ThreadHelper.ThreadStart(Object obj)…