This message contains attachments that are still being loaded. Are you sure you want to send it?

Lately, now in MacOS Sequoia 15.0 and for the last couple of months in the previous operating system, when I attempt to forward Mail to another person that has come with attachments, Mac mail has been giving me a warning message, "This message contains attachments that are still being loaded. Are you sure you want to send it?" If I answer the warning message box by clicking on "Send Anyway", it immediately pops up a caution box saying, "Cannot send message using the server XXX" where XXX is one of my email servers (e.g., @gmail.com or MobileMe). If I try to select one of the other email servers, it doesn't send. The only solution is to edit the email and delete the attachments that often are the very attachment I am purposefully trying to forward to another person. To add to this confusion, the mail sent sound is heard even when the email message has not really been sent yet. I content that sound should only be heard when the email is actually sent, not before a box pops up saying the email can't be sent. The only "fix" is to edit the message and delete the attachments in the message I am trying to forward which always have "downloading..." beneath their icon. The trouble is, the downloads mail is complaining about never complete, even leaving the app for a long period. Furthermore, why are they downloading anyway since they are already in my mail on my Macbook Pro? I have noted that while I can delete the "downloading..." attachments that causing the issue, I lose the ability to forward attachments to people, something that I need to be able to do with an email app.