There may be many reasons why attachments in Alimail cannot be downloaded, including but not limited to the following:

1. Network problem: An unstable or slow network connection may cause the attachment to fail to download.

2. Attachment size limit: Alimail may have a limit on the size of attachments. If the attachment exceeds the limit, it may not be downloaded.

3. Server problem: There may be a temporary problem with the Alimail server, resulting in the attachment being unable to download.

4. Permission problem: If the attachment is set with some specific permissions, such as only allowing specific users to download, it may prevent others from downloading.

5. Software problem: There may be a problem with the software on your computer or mobile phone, resulting in the inability to download the attachment correctly. To solve this problem, you can try the following methods:

1. Check the network connection: Make sure your network connection is stable and fast enough.

2. Check the size of the attachment: If the attachment is too large, try to compress or split the attachment.

3. Check the server status: Wait for a while and try to download the attachment again to see if it returns to normal.

4. Check the permission settings: If the attachment has specific permission settings, make sure you have enough permissions to download the attachment.

5. Update the software: Try to update the software on your computer or phone to see if it solves the problem. I hope the above content can help you solve the problem. If you have other questions, please feel free to ask me.