Changing this out is what moves us from the old system to the new one.
Instead of having a single channel manage a whole mailbox, we can now
specify an attribute set of groups that should correspond to an email
account.
Each of these groups contains an attribute set of channels that make
it up, and are grouped together for synchronization. In addition, each
of these channels can have additional IMAP4 parameters attached to
them to further refine synchronization.
Lastly, each of the channels is grouped together under the Group
section, ensuring that the channels' mailboxes synchronize as they
have been specified.
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