If the file doesn't pass validation, whoever sent it gets a clear error and nothing is saved. Common reasons: - **Type not allowed** for that channel (e.g. an executable). - **Content that doesn't match** the extension (a ".png" that isn't actually an image inside) — protection against disguised files. - **Too large**: 20 MB images · 25 MB audio · 50 MB documents and video. On Telegram, its own platform also caps attachments at 20 MB. - **Too many attachments** in the same message: the first ones are processed and it's honestly stated how many were left out.