private string BuildFullPathForAttachments(string partialPath)
{
if(partialPath == null) partialPath = "";
partialPath = partialPath.Replace("/", Path.DirectorySeparatorChar.ToString()).TrimStart(Path.DirectorySeparatorChar);
string up = Path.Combine(host.GetSettingValue(SettingName.PublicDirectory), AttachmentsDirectory);
return CheckPath(Path.Combine(up, partialPath), up); // partialPath CANNOT start with "\" -> Path.Combine does not work
}