IBM released the new Interim Fix 3 for IBM Notes 9.0.1 FP10 including the following bug fixes:

The IF3 is available at IBM Fix Central:

http://www.ibm.com/support/fixcentral/quickorder?product=ibm%2FLotus%2FLotus+Notes&fixids=Notes_901FP10IF3_W32_Standard&source=SAR

Today I received an Alert Flash regarding issues on IBM Notes/Domino Feature Pack 10 with the hint to stop upgrades. Currently the following issues are known:

• (fix available) The IBM Sametime client embedded within the IBM Notes client stops working after you install Notes 9.0.1 FP10 on top of Lotus Notes 9.0.1 FP9 + Sametime Embedded build 9.0.x clients
  http://www-01.ibm.com/support/docview.wss?uid=swg22012939

• (verified by L2) SMTP Mails with Umlauts broken after installing FP10                    This seems to be regression. Support is working.

• (verified) Group iQ.Suite – Out of License because the internal product numbering has changed. The API reports a different version number.
  Before upgrade eg 9.0.1.9.0.0  => 9.0.1 FP9, after upgrade 900.0.11.0.0.0  => 9.0.1 FP10
  Group is informed and can assist. Group will provide Hotfixes of iQ.Suite (19.1.5, 20.2.3 or 20.3) soon.

• (not yet verified) org.eclipse.core.runtime.CoreException: Plug-in http://com.ibm.domino.java .api was unable to load class http://com.ibm .domino.osgi.widgets.UpdateWidgetsTask.
  Also custom plugins are broken.

• (not yet verified) DOTS Task is crashing during startup (OSGI Plugins disappear), s.a.a.

• (not yet verified) Uninstall of FP10 not possible.
  From scratch reinstall required.

• (pending) Regarding Mailsploit, the remediation will be included in an FP10 interim fix. Development working on it through SPR #JBAMATTKY3.

So it´s suggested to stop upgrading your environment at the moment.