What's a Reasonable Inbox Size?

[Joseph Tam]

On Thu, 7 May 2020, Asai wrote:

> I have several users who have inboxes that are over 20 GB.
>
> As email admins,  how do you handle inboxes that are so large? Do you use 
> mailbox types that have better performance like dbox? We're using maildir.
>
> What's a reasonable inbox size?  Is 20+ GB reasonable and nothing to worry 
> about?

It depends on what you consider reasonable.

The processing time of file operation that iterates through a mailbox
will generally go up proportinately with size.  If you do a text search
without some indexing system like Solr, it will take a very long time.

If the mailbox is just some archive that you pile up and forget about it
except for once in a blue moon retrieval, then it might be reasonable.

If it's an active mailbox, it will be a pain to navigate, in the same
way a single folder with 100K files or a file cabinet with huge stacks
of envelopes.

I would guess some partioning of the large mailboxes into smaller
mailboxes would help with active mailboxes.  Most people spend most of
their time on new/recent messages, so making time or size or subject
based volmes wouldn't be a bad idea.

If the bulk of the size are redundant copies of attachments, then Dovecot's
*dbox support de-duping which would aso help.

Joseph Tam <jtam.home at gmail.com>