In Thunderbird's message list, we can configure which columns we would like to see. One of these columns is called "Attachments". If we configure the message list to show this column, a paperclip symbol is displayed for each message which contains attachments.
For me, this has never worked reliably, which is going to become a real pain now. In most cases (but not always), the paperclip symbol is not shown after I have received a message with an attachment. I have to open the message and close it again to have the paperclip symbol shown.
Even worse, if I move messages which have the paperclip symbol from my inbox to other folders, they may lose the paperclip symbol; that is, the symbol is no more shown in the message list in the other folders. To get it back again, I have to open the message in the other folder again; then the symbol is back.
I would like to know how to get around that. Even in the inbox, I'd like to see whether a message has an attachment before opening it; having to re-open a message in the new folder after having moved it just to get back the paperclip symbol is a no-go.
I am on TB 91.9.0 x64 / Windows 10 x64.
P.S. This question does not relate to encrypted messages.
Corrupt index files / folders shouldn't be the problem:
I have randomly picked some folders and have repaired them (Right-Click -> Properties -> Repair folder). This didn't change anything; the paperclip symbol was still missing for messages with attachments in these folders.
In the left pane, I have selected an account and have compacted it (File -> Compact Folders). According to everything I have read so far, this should compact and repair all folders which are listed in that account, because compaction includes repair. This didn't change anything. In folders in this account, messages with attachments were still missing the paperclip symbol.
If have deleted all .msf files in the respective Thunderbird profile and have waited until Thunderbird had downloaded all messages again. Again, this didn't improve the situation. In all accounts in all folders, messages with attachments were still missing the paperclip symbol.
I always fully synchronize all messages in all accounts (Tools -> Account Settings -> -> Sychronization & Storage -> Activate "Keep messages in all folders for this account on this computer").
I forgot to mention that all affected accounts are IMAP accounts. I have multiple PCs with multiple TB instances connected to the IMAP server, and the problems exists in each of the TB installations. Opening a message with an attachment on one PC and closing it again leads to the following situation: On that one PC, the paperclip symbol is shown for that message, but on the other PCs, it still is not shown.
I don't know if the same problem exists with POP3 accounts.
Update 4 (2022-06-11)
Motivated by the comments, I have tested TB 68 in this respect (the portable Windows version, configured to not synchronize messages, i.e. to not download them locally). The result:
TB 68 seems to show the paperclip symbol for every message which contains attachments. But there is the opposite problem: It shows the paperclip symbol even for messages which do not contain attachments.
When I then let a folder download locally in TB 68 (e.g.
Right-Click -> Properties -> Synchronization -> Download now), the paperclip symbols get adjusted and are correct afterwards. This is a thing I can live with because I normally let TB synchronize all folders. From a technical perspective, I can understand that in many cases TB may have to scan the whole message to decide whether or not it contains attachments.
So TB 68 behaves correctly (except when not having the folder synchronized).
For clarification, synchronizing a folder / downloading the messages in TB 91 does not have any effect. So we can say that TB 68 works correctly while TB 91 doesn't.
To be honest, I don't know whether I'll waste further time and test it with TB 78.