产品环境sql server database的mail发不出邮件，影响客户的业务，在数据库中进行诊断
诊断sql:
EXEC msdb.dbo.sp_send_dbmail
@profile_name = 'DB Messaging',
@recipients = 'jamesz@gmail.com',
@body = 'James_test_2019',
@body_format = 'HTML',
@subject = 'James_test_2019'
执行过后并没有收到邮件，查询event log表，也没有任何记录：
SELECT * FROM msdb.dbo.sysmail_event_log
ORDER BY log_id DESC
检查邮件的状态，都是unsent：
SELECT top 100 * FROM msdb.dbo.sysmail_allitems
ORDER BY send_request_date DESC
根据以下链接的建议进行诊断：
http://www.midnightdba.com/DBARant/complete-troubleshooting-guide-for-sql-server-databasemail-dbmail/
所有诊断项均正常。
同时检查sql server errorlog， windows event log和windows cluster log，发现周末出现的storage异常和mail功能失效关联端倪
The brief analysis for mail can't sent problem：
sql errorlog显示sql instance的恢复启动时间是 2019-10-25 11:04:50.050 CDT
但是在 windows cluster log, clussvc.exe 在时间段 2019/10/25-07:54:02.903 to 2019/10/25-16:04:18.499并没有记录
恰好在这段时间，storage 存储异常
之后sql instance在cluster service有问题的情况下启动工作
并且获取了本地local的信息而不是cluster service的信息.
windows event log显示，database mail通过连接. 到db而出现错误证明上述猜测
Server Name: ., Database Name: msdb
解决方案就是重启备用节点后，做一个干净状态的failover，让sql instance在正常的cluster service基础之上。
SQL Server Errorlog:
2019-10-25 11:04:50.050 Server Microsoft SQL Server 2014 (SP3-CU2) (KB4482960) - 12.0.6214.1 (X64) Feb 2 2019 01:10:18 Copyright (c) Microsoft Corporation Enterprise Edition: Core-based Licensing (64-bit) on Windows NT 6.3 <X64> (Build 9600: )
2019-10-25 11:04:50.050 Server UTC adjustment: -5:00
2019-10-25 11:04:50.050 Server (c) Microsoft Corporation.
2019-10-25 11:04:50.050 Server All rights reserved.
2019-10-25 11:04:50.050 Server Server process ID is 5700.
2019-10-25 11:04:50.050 Server System Manufacturer: 'Cisco Systems Inc', System Model: 'UCSB-B200-M3'.
2019-10-25 11:04:50.060 Server Authentication mode is MIXED.
2019-10-25 11:04:50.060 Server Logging SQL Server messages in file 'D:MSSQL12.MSSQLSERVERMSSQLLogERRORLOG'.
2019-10-25 11:04:50.060 Server The service account is 'TANsvc.DBAHFDN01VS.sql'. This is an informational message; no user action is required.
2019-10-25 11:04:50.060 Server Registry startup parameters: -d D:MSSQL12.MSSQLSERVERMSSQLDATAmaster.mdf -e D:MSSQL12.MSSQLSERVERMSSQLLogERRORLOG -l D:MSSQL12.MSSQLSERVERMSSQLDATAmastlog.ldf -T 3226
2019-10-25 11:04:50.060 Server Command Line Startup Parameters: -s "MSSQLSERVER"
2019-10-25 11:04:50.450 Server SQL Server detected 2 sockets with 10 cores per socket and 20 logical processors per socket, 40 total logical processors; using 40 logical processors based on SQL Server licensing. This is an informational message; no user action is required.
2019-10-25 11:04:50.450 Server SQL Server is starting at normal priority base (=7). This is an informational message only. No user action is required.
2019-10-25 11:04:52.180 spid9s The NETBIOS name of the local node that is running the server is 'DBAHFDN01N1'. This is an informational message only. No user action is required.
cluster log:
00002750.0000251c::2019/10/25-07:54:02.903 DBG [RCM] rcm::RcmResource::Control: (QUORUM_NEW, SWITCH_MONITORS)
00002750.00000ed8::2019/10/25-07:54:02.903 DBG [RCM] QUORUM_NEW: Ignoring reset because resource flag 2 is not set.
00002750.00000ed8::2019/10/25-07:54:02.903 DBG [RCM] QUORUM_NEW: Ignoring reset because resource flag 32 is not set.
00002750.0000251c::2019/10/25-07:54:02.903 DBG [RCM] Switch monitor call for QUORUM_NEW when there were pending controls, enqueuing the switch
00002750.0000251c::2019/10/25-07:54:02.903 DBG [RCM] Pending controls for QUORUM_NEW are empty now but we're not in a state that can switch monitors; removing SWITCH_MONITORS control.
00002750.00000ed8::2019/10/25-07:54:02.903 DBG [RCM] rcm::RcmGroup::ComputeFailoverThreshold=> (Cluster Group, 0, computed)
00002750.00000ed8::2019/10/25-07:54:02.903 DBG [RCM] rcm::RcmResource::StmPreOnlineCheck(QUORUM_NEW)
00000b4c.00000b50::2019/10/25-16:04:18.499 INFO -----------------------------+ LOG BEGIN +-----------------------------
00000b4c.00000b50::2019/10/25-16:04:18.499 INFO [CS] Starting clussvc as a service
00000b4c.00000b50::2019/10/25-16:04:18.499 INFO [CS] cluster service logging level is 5
00000b4c.000009cc::2019/10/25-16:04:18.546 INFO [CS] Creating cluster node <vector len='1'>
00000b4c.000009cc::2019/10/25-16:04:18.546 INFO <item>ClusSvc</item>
00000b4c.000009cc::2019/10/25-16:04:18.546 INFO </vector>
00000b4c.000009bc::2019/10/25-16:04:18.546 INFO [StartupConfig]: Initializing.
Windwos event log:
10/30/2019 12:05:03 PM
1) Exception Information
===================
Exception Type: Microsoft.SqlServer.Management.SqlIMail.Server.Common.BaseException
Message: There was an error on the connection. Reason: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server), connection parameters: Server Name: ., Database Name: msdb
Data: System.Collections.ListDictionaryInternal
TargetSite: Void OpenConnection(Microsoft.SqlServer.Management.Common.SqlConnectionInfo)
HelpLink: NULL
Source: DatabaseMailEngine
StackTrace Information
===================
at Microsoft.SqlServer.Management.SqlIMail.Server.DataAccess.ConnectionManager.OpenConnection(SqlConnectionInfo connectionInfo)
at Microsoft.SqlServer.Management.SqlIMail.Server.DataAccess.DataAccessAdapter.OpenConnection(String dbServerName, String dbName, String userName, String password, String appName, Int32 connectionTimeout)
at Microsoft.SqlServer.Management.SqlIMail.Server.DataAccess.DataAccessAdapter.OpenConnection(String dbServerName, String dbName, String userName, String password, Int32 connectionTimeout)
at Microsoft.SqlServer.Management.SqlIMail.IMailProcess.QueueItemProcesser.ProcessQueueItems(String dbName, String dbServerName, Int32 lifetimeMinimumSec, LogLevel loggingLevel, Byte[] encryptionKey, Int32 connectionTimeout)
2) Exception Information
===================
Exception Type: System.Data.SqlClient.SqlException
Errors: System.Data.SqlClient.SqlErrorCollection
Class: 20
LineNumber: 0
Number: 2
Procedure: NULL
Server:
State: 0
Source: .Net SqlClient Data Provider
ErrorCode: -2146232060
Message: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
Data: System.Collections.ListDictionaryInternal
TargetSite: System.Data.ProviderBase.DbConnectionInternal GetConnection(System.Data.Common.DbConnection)
HelpLink: NULL
StackTrace Information
===================
at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject)
at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
at System.Data.SqlClient.SqlConnection.Open()
at Microsoft.SqlServer.Management.SqlIMail.Server.DataAccess.ConnectionManager.OpenConnection(SqlConnectionInfo connectionInfo)