FT_Index_Ignore_Attachment_Types 

Explanation:
notes.ini FT_Index_Ignore_Attachment_Types debuted in Notes/Domino 5.0.5, and lets administrators specify additional file types to ignore in the indexing of attachments. For example, the line
FT_Index_Ignore_Attachment_Types=*.tif
tells the indexer not to index attachments with the TIF extension. This can reduce the size of the full text index and speed the return of search results. To specify multiple file types to be ignored, separate them with a comma.

Default:
Since release 5.0.5, Notes/Domino ignores the following types of files when indexing attachments by default:
.NSF
.NTF
.SYS
.PAG
.IMG
.WAV
.GIF
.JPG
.DLL
.TAR
.EXE
.ZIP
.AU
.MPG
.MOV
.MP3

Recommendation:
Use this parameter to reduce the full text indexer load and improve performance.

Restarts:
The Domino server must be restarted after modifying this setting.

References:
Technote 1092445: Domain Indexer is indexing file types disabled via FT_INDEX_IGNORE_ATTACHMENT_TYPES

Domino Configuration Tuner:
This setting is included in the DCT catalog of best practices.