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Old 25 May 2019, 09:51 PM   #10
JeremyNicoll
Senior Member
 
Join Date: Dec 2017
Location: Scotland
Posts: 111
I'm impressed that Inbox's technical support people provided a thorough answer.

It seems they've optimised their system for users of their webmail systems, which is fair enough.

The problem with IMAP seems to be that /if/ your client requests downloads in chunks, the Inbox backend system is very inefficient. I can't quite see why anyone would design a system that says: the user wants an attachment (in chunks) so over & over again we'll do a lot of work... I would have expected their system to do the work once, cache the re-encoded attachment file, hand it out in chunks, and destroy it afterwards.

I think you should ask Thunderbird support whether there's a way to make sure that an IMAP account in TB does not request data in chunks, or perhaps only does so if the attachment size is above some threshhold (maybe a lot bigger than most of your attachments). You have a fairly fast connection and presumably it's pretty reliable - not dialup on a flakey connection - so needless chunking (so that chunks can be re-requested shouldn't be needed). See: https://lists.mozilla.org/listinfo/support-thunderbird

If that's not possible in TB then I'd suggest you try a POP3 session, just for retrieval of attachments. POP3 is a simple protocol and it just asks for the entire contents of an email in one operation. I don't know enough about TB to know if you'd change the existing account from IMAP to POP3 and then back again (I suspect not though, as that might screw up IMAP flags). More likely you'd disable the IMAP account (ie leave it defined), define a new POP3 account for the same server, then use it to grab the whole of the mails concerned. You might have a problem pointing the POP3 server at the mails concerned as POP3 might just see those in the Inbox account's inbox, not other folders as well. You might also need to tell POP3 to leave the mails on the server (at least while experimenting).
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