Why is my MacBook Pro (late 2013, Retina) crashing? So...my Mac had a spinning beach ball of death (SBBOD), and has been having these about once a day for the past two weeks. :-( 

I manually turned off my computer (held power key), waited ~3 minutes, then rebooted. I went straight to Console to figure out what was up, since it's the place to look for crash reports. 

I looked there under "All Messages", and found the last few messages before my reboot: 

Here are the last half-dozen or so lines: 

10/1/15 11:26:05.493 AM sharingd[291]: 11:26:05.493 : SDActivityAdvertiser::continuity:didFailToStartAdvertisingOfType:withError: Activity (The operation couldn’t be completed. (com.apple.identityservices.error error 200.))
10/1/15 11:26:07.340 AM sharingd[291]: 11:26:07.339 : SDActivityAdvertiser::continuity:didFailToStartAdvertisingOfType:withError: Activity (The operation couldn’t be completed. (com.apple.identityservices.error error 200.))
10/1/15 11:26:07.340 AM sharingd[291]: 11:26:07.340 : SDActivityAdvertiser::continuity:didFailToStartAdvertisingOfType:withError: Activity (The operation couldn’t be completed. (com.apple.identityservices.error error 200.))
10/1/15 11:26:07.389 AM WindowServer[168]: _CGXGetWindowMovementGroup: Operation on a window 0x19 requiring rights 0x5 by caller Dashboard
10/1/15 11:26:07.389 AM DashboardClient[1057]: _NXMoveWindow: error moving window (1000)
10/1/15 11:26:11.638 AM SubmitDiagInfo[416]: SubmitDiagInfo sucessfully uploaded 117 diagnostic messages
10/1/15 11:26:11.668 AM SubmitDiagInfo[416]: Submitted problem report file:///Users/ME/Library/Logs/DiagnosticReports/com.apple.MailServiceAgent_2015-09-30-123002_MY-MacBook-Pro.crash
10/1/15 11:26:16.706 AM sharingd[291]: 11:26:16.705 : SDActivityAdvertiser::continuity:didFailToStartAdvertisingOfType:withError: Activity (The operation couldn’t be completed. (com.apple.identityservices.error error 200.))
10/1/15 11:29:12.000 AM bootlog[0]: BOOT_TIME 1443724152 0


(Note: I changed my username to ME and computer name to MY-MacBook-Pro for anonymity.) 

This led me to read the crash log at /Users/ME/Library/Logs/DiagnosticReports/com.apple.MailServiceAgent_2015-09-30-123002_MY-MacBook-Pro.crash. Here are the most relevant pieces of information: 

Process:               com.apple.MailServiceAgent [524]
Path:                  /System/Library/PrivateFrameworks/MailService.framework/Versions/A/XPCServices/com.apple.MailServiceAgent.xpc/Contents/MacOS/com.apple.MailServiceAgent
Identifier:            com.apple.MailServiceAgent
Version:               8.2 (2104)
Build Info:            Mail-2104000000000000~1
Code Type:             X86-64 (Native)
Parent Process:        ??? [1]
Responsible:           com.apple.MailServiceAgent [524]
User ID:               501

Date/Time:             2015-09-30 12:30:01.204 -0700
OS Version:            Mac OS X 10.10.5 (14F27)
Report Version:        11
Anonymous UUID:        [I am omitting this too :-)]


Time Awake Since Boot: 280 seconds

Crashed Thread:        2  Dispatch queue: NSOperationQueue 0x608000030940 :: NSOperation 0x608000243090 (QOS: LEGACY)

Exception Type:        EXC_CRASH (SIGABRT)
Exception Codes:       0x0000000000000000, 0x0000000000000000

Application Specific Information:
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Append action must have account'
terminating with uncaught exception of type NSException
abort() called


What's going on? From the look of it, Mail is crashing because I don't have an account. That makes no sense. If I don't have an account, there shouldn't be activity, right? 

How can I fix this, besides creating an account?
Started as a comment, but got too long. You are asking two questions. The "spinning beach ball of death" and the crashing MailServiceAgent are most likely unrelated.

To clarify. The "spinning beach ball of death" doesn't actually indicate that anything is crashing. It indicates that an application (most of the time, temporarily) is not responding to messages from the operating system.

From Apple's Human Interface Guidelines:


  The spinning wait cursor is also standard, but it is displayed
  automatically by the window server when an app can't handle all of the
  events it receives. In general, if an app doesn’t respond for a few
  moments, the spinning wait cursor appears. If the app continues to be
  unresponsive, users often react by force-quitting it.


If you move the cursor around, does the wait cursor still appear if it is over another application or over your desktop? If you ALT+TAB to bring another application to the foreground do you still get the wait cursor? If it only appears over one application then that application alone is having an issue. If it appears over all applications or if you find you are unable to move the cursor or to ALT+TAB to another application then you have a wider system problem rather than a problem with one specific application.