Installing IE8 on a machine with the R8.5 client will cause any opened external mail(internal mail seems fine) to take about 60seconds (or more) to display the message and the client locks up until displayed (this also happens if you have the preview pane open).
Deinstalling IE8 and go back to IE7 fixes the issue.
I test installed IE8 on another machine and was able to reproduce the slow done, and removing it brought it back to normal functionality.
So if you have clients that left the IE8 auto update run and are complaining about slow display of external email check for IE8.
Laine
Subject: Thanks to Edward de Leau
Cause :It will happen when you install Lotus Notes 8.5 Standard / Eclipse Edition & Internet Explorer 8. If you have process monitor installed, you can view that notes2.exe will check all sites (Restricted Sites) are in Internet Explorer 8 internet settings. After that notes2.exe do query open in file “C:\Program Files\IBM\Lotus\Notes\framework\rcp\eclipse\plugins\org\eclipse\osgi\framework\internal\protocol\about\Handler.class” but the result is not found repeatly (may be hundred times according the restricted sites amount). Then the email will be opened after 1-2 minutes query.
Solution :
<< Backup your registry before delete some keys >>
You have to delete all Restricted Sites list from Internet Explorer settings in Tools - Internet Options - Security - Restricted Sites - Sites. Or you can remove the list manually from registry in HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains & \EscDomains & \Ranges. Also remove in HKLM\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap.
Subject: Preference
In addition to downgrading IE, you can try the preference in Notes Basic Client Config “Disable embedded browser for MIME messages”, this will force the client to render HTML email using perweb (internal to notes)