I think that doesn’t apply in this case. The email client is just an IMAP client and any directory is only caching some of what is on the IMAP server - and there could be a setting to limit, directly or indirectly, the amount of space used in caching. On the other hand, Geary is notoriously free of settings so maybe there isn’t such a setting.
What you really need to control is the IMAP server i.e. the bridge software. So the question arises as to whether you can control where the IMAP server locates its message store.
If neither piece of software gives you adequate control then you could end up with two copies of every email, consuming space on the eMMC drive.
I don’t have extensive knowledge of mail clients and their inner workings, I’ve been using Thunderbird almost exclusively for many years. Certainly with Thunderbird, the out the box behaviour is to sync everything with the IMAP server, you essentially end up with a local copy of all mails which is then kept in sync local <> server. Within Thunderbird’s account settings there is a “Local directory” setting to specify a directory on the local machine for mail storage. Thunderbird also has “Synchronization & Storage” options where you can fine tune how much mail data is stored locally.
When I used mail on mobile devices, I used K9 on Android, out the box this was the opposite to Thunderbird in that it downloaded very little mail data, just the headers of recent mails but it also had many settings to fine tune how much or little mail data is stored locally.
Geary is a desktop mail client, I’ve looked at it a couple of times but have always concluded it to be too primitive for my needs and I also noted that it was very feature thin with little to no real options/settings. I don’t know as I don’t use it, but given it’s limited configuration that I have observed previously, I’d suspect it probably has similar out the box behaviour to thunderbird in that it just grabs everything and ends up with a local copy of all mail?
The Proton Mail Bridge, is exactly that, a simple bridge, it does not store or cache any mails (or it never used to, I can’t imagine that behaviour has changed but maybe).
Indeed. Thunderbird gives a level of control approximately on par with what I would like i.e. restrict by age and size (but doesn’t seem to allow a blanket control over the total disk space allocated to caching a given account).
Yes. Not a lot of control overall, directly or indirectly, over the disk space allocated to caching. It seems to me that the only real control is the “Trash” icon but see next. Certainly that’s the way I use it on the Librem 5.
Unfortunately it uses an SQLite database for its cache (apart from attachments?). So I wouldn’t expect disk space usage necessarily to go down even when you delete messages - and I can see in the database rows corresponding to messages that I deleted long ago - and that’s not great for privacy either potentially.
No. Because these are undeleted rows in the table of messages. (It could just be a bug because we are running a fairly old version of Geary.)
If the rows had been deleted then, yes, vacuum;
or maybe (untested) pragma auto_vacuum=full;
I resile from just deleting the rows myself as I have limited internals knowledge of Geary and I don’t really want to break it.
A hack way, as Geary only supports IMAP, would be to delete the mail account in Geary and create a new account - since it would then (presumably) recreate and resynch the local account cache database completely against the IMAP server. (I can confirm absolutely that the old messages do not exist on the server any more.)
When I reflash to crimson I will probably do that i.e. propagate the Geary account settings but not propagate the SQLite database (or any other Geary files). So that may well solve the problem for me.
So, yes, vacuum is a part of the privacy and security puzzle but not the story in this case (and not the whole story).
