Backup tool failed

em client backup tool failed and it instructed me to send the following text to support:
System.IO.IOException: database or disk is full —> System.Data.SQLite.SQLiteException: database or disk is full
   at System.Data.SQLite.SQLiteBlob.Read(Byte[] buffer, Int32 count, Int32 offset)
   at MailClient.Storage.Data.BlobStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   — End of inner exception stack trace —
   at MailClient.Storage.Data.BlobStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at MailClient.Streams.StreamHelper.CopyStream(Stream inputStream, Stream outputStream, Nullable`1 cancellationToken, ProgressReporter reporter)
   at MailClient.Storage.Data.DatabaseCopyTool.CopyContents(Table table, Boolean sortDesc)
   at MailClient.Storage.Data.DatabaseCopyTool.CopyTableData(Table table)
   at MailClient.Storage.Data.DatabaseCopyTool.CopyInternal(String specificTable, Boolean copyIndexesViewsAndTriggers)
   at DbBackup.FormBackup.Backup(CancellationToken cancellationToken)
   at DbBackup.FormBackup.<mainform_load>b__27_0(Object a, DoWorkEventArgs b)
at System.ComponentModel.BackgroundWorker.OnDoWork(DoWorkEventArgs e)
at System.ComponentModel.BackgroundWorker.WorkerThreadStart(Object argument)
Data:
Table: LocalMailContents</mainform_load>