ProviderOperation: "SendSingleMessage" | "GetMessages" | "GetSingleMessage" | "ForwardMessage" | "ReplyToMessage" | "CreateDraft" | "DeleteMessage" | "MoveMessage" | "ListFolders" | "MarkAsRead" | "ArchiveMessage" | "SearchMessages" | "ListAttachments" | "DownloadAttachment"

Enumeration of all supported provider operations. Use with getSupportedOperations() to discover provider capabilities.