How do I consistently place attachments at the end of outgoing emails in Mail on iMac?

Hey! I understand your frustration with this unintended behavior. I just tried it on Tahoe 26.1 and experienced no issues.

I recognize that you are running an older version of MacOS and would recommend to check if you are on the most recent version available for your system. Apart from that, I always recommend using Apple's Feedback Portal (Feedback - Apple.com Website - Apple) to report these. Remember to include your MacOS Version as context.

Until it's fixed- you might already know this, but you can place and position the attachments yourself by looking for the line indicating the insertion point while drag/dropping the file into the mail. You can also move an already placed attachment by selecting it, and dragging it through the mail.

I hope I could be of help and wish you all the best

I think you need to add some details as to how you're attaching the files.

For example, are you dragging files from your desktop into the mail message?

Are you using the Attachment icon in the toolbar to choose a file to attach?

Are you using the File -> Attach Files menu item?

Are you dragging Photos from the Photo browser?

Something else?

Ultimately, at least as far as I can tell, all of these should work consistently - namely the file chooser options (toolbar or menu) will insert the file at the current insertion point, and the drag-and-drop options put the file wherever you drop them.

To be honest, I can't see that the menu option for Always Insert Attachments at End of Message has any effect at all.

I would have thought that once you finished the email text that you would place the cursor below the text and hit return a few times to give the attachment some room to embed it's self into the email.

Send large attachments in Mail on Mac

Add attachments to emails in Mail on Mac - Apple Support (CA)

How an attachment is viewed is under the control of the recipient and their email client settings. If you send me an email with an attachment I will never see it in the body of the email. Maybe you are overly worried about something that in the end is out of your control.