Hi Eric, thanks for the link.... very useful app, will need to make a donation (thought shareware was dead!!).
Here's what it found (I shut MS Outlook and tried opening Mail but after a minute or so it quit).
EtreCheck version: 3.4.6 (460)
Report generated 2017-10-21 12:32:09
Download EtreCheck from https://etrecheck.com
Runtime: 1:32
Performance: Excellent
Click the [Lookup] links for more information from Apple Support Communities.
Click the [Details] links for more information about that line.
Click the [Clean up] link to delete unused files.
Problem: Beachballing
Hardware Information: ⓘ
iMac (Retina 5K, 27-inch, 2017)
[Technical Specifications] - [User Guide] - [Warranty & Service]
iMac - model: iMac18,3
1 3.8 GHz Intel Core i5 (i5-7600K) CPU: 4-core
8 GB RAM Upgradeable - [Instructions]
BANK 0/DIMM0
4 GB DDR4 2400 MHz ok
BANK 0/DIMM1
Empty
BANK 1/DIMM0
4 GB DDR4 2400 MHz ok
BANK 1/DIMM1
Empty
Handoff/Airdrop2: supported
Wireless: en1: 802.11 a/b/g/n/ac
iCloud Quota: 4.63 GB available
Video Information: ⓘ
Radeon Pro 580 - VRAM: 8192 MB
iMac 5120 x 2880
Disk Information: ⓘ
APPLE HDD ST2000DM001 disk1: (2 TB) (Rotational)
[Show SMART report]
EFI (disk1s1 - MS-DOS FAT32) <not mounted> [EFI]: 210 MB
(disk1s2) <not mounted> [CoreStorage Container]: 2.00 TB
Recovery HD (disk1s3 - Journaled HFS+) <not mounted> [Recovery]: 650 MB
APPLE SSD SM0128L disk0: (121.33 GB) (Solid State - TRIM: Yes)
(disk0s1) <not mounted> [EFI]: 315 MB
(disk0s2) <not mounted> [CoreStorage Container]: 120.88 GB
(disk0s3) <not mounted> [Boot]: 134 MB
USB Information: ⓘ
USB30Bus
Western Digital My Passport 07A8
My Passport 07A8 disk4: (1 TB)
EFI (disk4s1 - MS-DOS FAT32) <not mounted> [EFI]: 210 MB
Backup (disk4s2 - Journaled HFS+) /Volumes/Backup : 999.83 GB (271.55 GB free)
Broadcom Corp. Bluetooth USB Host Controller
Apple Inc. FaceTime HD Camera (Built-in)
USB31Bus
Thunderbolt Information: ⓘ
Apple Inc. thunderbolt_bus
Drobo Mini
G-Technology ev All-Terrain Case Thunderbolt
HGST HTS721010A9E630 disk3: (1 TB) (Rotational)
[Show SMART report]
EFI (disk3s1 - MS-DOS FAT32) <not mounted> [EFI]: 210 MB
G-DRIVE ev ATC with Thunderbolt (disk3s2 - Journaled HFS+) /Volumes/G-DRIVE ev ATC with Thunderbolt : 999.86 GB (555.47 GB free)
Virtual disks: ⓘ
Macintosh HD (disk2 - Journaled HFS+) / [Startup]: 2.11 TB (1.43 TB free)
Physical disk: disk0s2 120.88 GB Online
Physical disk: disk1s2 2.00 TB Online
Drobo (disk5s2 - Journaled HFS+) /Volumes/Drobo : 17.59 TB (16.08 TB free)
Physical disk: Mini - TB 17.59 TB (16.08 TB free)
System Software: ⓘ
macOS Sierra 10.12.6 (16G29) - Time since boot: about one hour
Gatekeeper: ⓘ
Mac App Store and identified developers
Clean up: ⓘ
/Library/LaunchAgents/com.synology.PhotoUploaderFinderSync.plist
/Applications/Synology Photo Station Uploader.app/Contents/MacOS/contextmenu/PhotoUploaderShellApp.app/Contents/MacO S/PhotoUploaderShellApp
Executable not found!
One orphan file found. [Clean up]
Kernel Extensions: ⓘ
/Library/Extensions
[loaded] com.TrustedData.driver.VendorSpecificType00 (1.8.0 - SDK 10.10) [Lookup]
[loaded] com.drobo.SCSI.ThunderBolt (1.2 - SDK 10.10) [Lookup]
System Launch Agents: ⓘ
[not loaded] 6 Apple tasks
[loaded] 174 Apple tasks
[running] 105 Apple tasks
System Launch Daemons: ⓘ
[not loaded] 39 Apple tasks
[loaded] 173 Apple tasks
[running] 105 Apple tasks
Launch Agents: ⓘ
[running] com.fujitsu.pfu.ScanSnap.AOUMonitor.plist (? 1d61e789 d066f2d5 - installed 2017-09-16) [Lookup]
[failed] com.synology.PhotoUploaderFinderSync.plist (? 3e95a14e 0 - installed 2017-09-19) [Lookup] - /Applications/Synology Photo Station Uploader.app/Contents/MacOS/contextmenu/PhotoUploaderShellApp.app/Contents/MacO S/PhotoUploaderShellApp: Executable not found!
[loaded] com.synology.SynoSIMBL_RefreshFinder.plist (Apple, Inc. - installed 2017-09-19)
Launch Daemons: ⓘ
[running] com.datarobotics.ddservice64d.plist (Drobo, Inc. - installed 2017-09-20) [Lookup]
[running] com.microsoft.autoupdate.helper.plist (Microsoft Corporation - installed 2017-10-12) [Lookup]
[loaded] com.microsoft.office.licensingV2.helper.plist (Microsoft Corporation - installed 2017-09-02) [Lookup]
User Login Items: ⓘ
DDAssist Application
(/Applications/Drobo Dashboard.app/Contents/Resources/DDAssist.app)
ATLoginItemHelper Plus SMLoginItem - Hidden (Apple, Inc. - installed 2017-09-15)
(/Applications/DrCleanerProPlus.app/Contents/Library/LoginItems/ATLoginItemHelp er Plus.app)
Internet Plug-ins: ⓘ
QuickTime Plugin: 7.7.3 (installed 2017-09-15)
Safari Extensions: ⓘ
[disabled] URL Advisor - Kaspersky Lab - http://kaspersky.com (installed 2017-09-17)
3rd Party Preference Panes: ⓘ
None
Time Machine: ⓘ
Skip System Files: NO
Mobile backups: OFF
Auto backup: YES
Volumes being backed up:
Macintosh HD: Disk size: 2.11 TB Disk used: 683.18 GB
Destinations:
Backup [Local]
Total size: 999.83 GB
Total number of backups: 27
Oldest backup: 10/10/2017, 11:59
Last backup: 21/10/2017, 11:52
Size of backup disk: Too small
Backup size 999.83 GB < (Disk used 683.18 GB X 3)
Top Processes by CPU: ⓘ
8% Mail
5% kernel_task
3% WindowServer
2% quicklookd
2% mds
Top Processes by Memory: ⓘ
1.03 GB kernel_task
240 MB com.apple.WebKit.WebContent
99 MB Safari
98 MB Dock
93 MB WindowServer
Top Processes by Network Use: ⓘ
Input Output Process name
1 MB 102 KB mDNSResponder
31 KB 10 KB netbiosd
8 KB 11 KB apsd
432 B 672 B ntpd
0 B 306 B DDService64d
Top Processes by Energy Use: ⓘ
4.04 WindowServer
1.72 DDService64d
0.64 com.apple.WebKit.WebContent
0.46 DDAssist
Virtual Memory Information: ⓘ
4.83 GB Available RAM
3.23 GB Free RAM
3.17 GB Used RAM
1.60 GB Cached files
0 B Swap Used
Software installs (last 30 days): ⓘ
GraphicConverter 10: 10.5 (installed 2017-09-21)
CardMinder: (installed 2017-09-23)
Noiseless: 1.3.2 (installed 2017-09-26)
Microsoft Remote Desktop: 8.0.27325 (installed 2017-10-01)
Duplicate Finder and Remover: 1.3.0 (installed 2017-10-04)
Duplicate File Finder: 4.3 (installed 2017-10-06)
Duplicate File Finder: 4.3 (installed 2017-10-06)
Drobo Dashboard: (installed 2017-10-09)
Microsoft Outlook for Mac: (installed 2017-10-11)
Microsoft PowerPoint for Mac: (installed 2017-10-11)
Microsoft OneNote for Mac: (installed 2017-10-11)
Microsoft AutoUpdate: (installed 2017-10-12)
Microsoft Excel for Mac: (installed 2017-10-12)
Microsoft Word for Mac: (installed 2017-10-12)
Sparkle: 2.2.3 (installed 2017-10-12)
Install information may not be complete.
Diagnostics Events (last 3 days for minor events): ⓘ
2017-10-21 09:49:28 Mail.app Hang [Open]
2017-10-19 22:45:00 com.apple.WebKit.WebContent High CPU use [Open] [Details]
2017-10-18 19:20:41 GraphicConverter 10.app Crash [Open]
Cause: Performing @selector(renameSelectedFiles:) from sender NSMenuItem 0x6000002b6a40
2017-10-18 18:33:25 cloudd Crash [Open]
Cause: *** Terminating app due to uncaught exception 'NSGenericException', reason: 'Failed to step (6922): "select apsEnvironment, isApplication, isCKSystemService, canMasquerade, canSetEnvironment, allowCustomAccounts, canAccessProtectionData, canSetDeviceIdentifier, hasAccessDuringBuddy, hasLightweightPCS, hasTCCAuthorization, allowsPowerNapScheduling, isOOPUI, allowsParticipantPII, displaysSystemAcceptPrompt, appIdentifier, clientPrefix from AppBundle where appBundleIdentifier = ? AND sourceAppBundleIdentifier = ?" - errcode:1b0a, msg:"disk I/O error", size: (null), path:/Users/USER/Library/Caches/*/CloudKitMetadata, fs:(null)/(null)'
abort() called
terminating with uncaught exception of type NSException