Indices
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EnhanceMail can keep full-text indices for some or all of your mailboxes.  Keeping such an index has a number of disadvantages as well as an advantage, so you'll probably only want to do this for some of your mailboxes.

Disadvantages
·	Creating an index for a large mailbox can take several minutes.
·	An index consumes between 15% (for large mailboxes) and 50% (for small mailboxes) of the disk space used by the mailbox file itself.
·	Opening, closing, and transferring messages to an indexed mailbox will be slightly slower than for a non-indexed mailbox.

Advantage
·	Finding all messages which contain a given set of words is nearly instantaneous even for huge mailboxes.

For example, the author has a mailbox 35.5 MBytes in size with 11620 messages.  Regular search for a word through the entire mailbox takes more than one minute.  A full-text index adds 4.6 MBytes in size to the mailbox, but with it finding all 240 messages which contain one word takes less than 5 seconds and finding all 3 messages which contain another word takes less than 1 second.

Creating an index
To create an index select the item Index in the Mailboxes menu and wait.  You can recognize mailboxes with indices by visual hints in the Mailbox window.
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Searching with the index
Searching is completely transparent.  Just open the Find panel, select Messages as Find Scope and search as usual.  If the mailbox has an index, Find will automatically use it to accelerate the search.  Regular expression searches and searches with Summaries as Find Scope are not accelerated or in any other way affected.

There are two small semantic changes to searches using the index.  Index searches will only search the content of messages, not the headers.  Also, index searches will only find complete words, not word fragments.  In this regard it is identical to the Digital Librarian.
(Known bug:  Under some circumstances EnhanceMail will not index rich NeXTmail messages)

Apart from that all capabilities of Find are preserved when doing index searches.  In particular, focused searches and automatic focusing with Find All continues to work and becomes much more useful with indices.  For more information, check out Mail Help.

Deleting an index
If at some point you wish to get rid of an index, select the item Delete Index in the Mailboxes menu or compact the mailbox.  The latter will also delete the index as compacting jumbles the messages sufficiently that maintaining the index becomes very difficult.  For that reason auto-compact will not compact indexed mailboxes.

Corrupt indices
The indices were designed to be robust, even under mistreatment.  For example, they will work correctly in combination with appnmail from the mailapp-utilities.  However, it is possible to cause the index to go out of sync with the mailbox file, for example by manipulation of mailbox files in the shell.  In that case, index searches will give erroneous results.  If you suspect that this has happened to one of your mailboxes, delete the index and recreate it.  No information will be lost and index will always be brought back into sync.
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