IBM announced that Lotus Notes/Domino 8.5.1 FP5 packages are ready to be downloaded. The fix pack contains several critical fixes and is recommended for all 8.5.1 users. It is also incremental and contains all fixes in prior fix-packs.

Fix list contained by FP4 can be seen on:
http://www-10.lotus.com/ldd/R5FixList.nsf/WhatsNew/f6845493d26dccb08525778f004e421a?OpenDocument

To download FP5:
http://www-01.ibm.com/support/docview.wss?uid=swg24025721