Missing attachment "paper clip" icon in Mac Mail

jszrules wrote:

Ever since the release of Sierra, and continuing into Mojave, the "paper clip" column in Mail has never shown a paper clip icon for incoming POP account messages that actually contain attachments. The attachments are still there in the email, but the paper clip indicator in the Mailbox view is just missing.

Is this both in the new 3 column view and in classic view?

Yes, I still have a similar issue, but it only occurs with the Inbox and from approx Sept 2016 onwards, prior to that date the "paperclip" is still present, but for Sent it continues to show even for the most recent messages.

Like you this was first noticed a couple of OS's back, I've tried deleting the Inbox mailbox and then importing back in again, changing views in the Mail App and rebooting into Safe Mode, nothing has worked.

I also have a POP account, strangely if I export the content as an mbox, then import on my old Snow Leopard Laptop the "paperclip" reappears in that Mail App, so it's OS related (ie it's not been stripped out of the message content itself).

I've basically given up, having raised a Bug Report with Apple which only resulted in a "Duplicate" response (ie others have also reported same) and never seeing mention of a fix under any subsequent OS update notes to date I've just accepted this is now how it will be. You might even find a few of my old forum posts hanging around, but no one back then had a fix other than to try IMAP.

Why Outgoing still works when Incoming doesn't may be due to the fact Outgoing for POP still employs the SMTP Server similar to an IMAP account, it's only Incoming that's different which solely uses a POP Server, if you follow my drift.

Anyhow, best of luck, not sure this can/or will get resolved but may be someone will come along with some additional ideas.

jszrules wrote:

Hi - yes, problem exists in both views.

Have you rebuilt the problem mailbox?

Mail>Mailbox>Rebuild

Rebuild mailboxes in Mail on Mac - Apple Support