Questions Trouble Setting Up a System Email Account

I have 2 tenants in our Acumatica install (single server). Test and Live. On our Test tenant I was able to get a System Email account added, setup and working perfect. However on our Live tenant, after mirroring exactly the account on the Test tenant, after clicking the TEST button, it just spins, and the Elapsed Time just keeps counting. 

I've triple checked the system email account settings, everything matches.

Some notes:

The spinner "Press to abort", does nothing.

System Management -> System Monitor does show the running process. However the ABORT button does nothing. If I click Active Threads, it shows this error in the modal that pops up:

User: xxx
Screen: ~/pages/sm/sm204002.aspx
Command: checkEMailAccount
Time, sec: 750
at System.Net.UnsafeNclNativeMethods.OSSOCK.recv(IntPtr socketHandle, Byte* pinnedBuffer, Int32 len, SocketFlags socketFlags)
at System.Net.UnsafeNclNativeMethods.OSSOCK.recv(IntPtr socketHandle, Byte* pinnedBuffer, Int32 len, SocketFlags socketFlags)
at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags, SocketError& errorCode)
at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
at PX.Common.IO.SmartStream.a(Boolean A_0, BufferCallback A_1) in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 64230
at PX.Common.IO.SmartStream.ReadLine(ReadLineAsyncOP op, Boolean async) in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 63092
at PX.Common.IMAP.Client.ImapClient.OnConnected() in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 101114
at PX.Common.TCP.TcpClient.OnConnected(CompleteConnectCallback callback) in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 66629
at PX.Common.TCP.TcpClient.ConnectAsyncOP.c() in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 65490
at PX.Common.TCP.TcpClient.ConnectAsyncOP.Start(TcpClient owner) in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 65295
at PX.Common.TCP.TcpClient.ConnectAsync(ConnectAsyncOP op) in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 66345
at PX.Common.TCP.TcpClient.Connect(IPEndPoint localEP, IPEndPoint remoteEP, Boolean ssl, RemoteCertificateValidationCallback certCallback) in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 66285
at PX.Common.TCP.TcpClient.Connect(IPEndPoint localEP, IPEndPoint remoteEP, Boolean ssl) in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 66239
at PX.Common.TCP.TcpClient.Connect(String host, Int32 port, Boolean ssl) in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 66189
at PX.Common.Mail.MailReceiver.ImapReceiver.a() in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 120511
at PX.Common.Mail.MailReceiver.ImapReceiver.Test() in C:\Users\svc-builder\AppData\Local\Temp\~PX.Comm.0\PX.Common.dll.il:line 120502
at PX.SM.EMailAccountMaint.a(Action A_0, String A_1) in C:\Bld2\AC-FULL2019R19-JOB1\Sources\NetTools\PX.Data\Maintenance\SM\EMailAccountMaint.cs:line 295
at PX.SM.EMailAccountMaint.b(IEnumerable`1 A_0) in C:\Bld2\AC-FULL2019R19-JOB1\Sources\NetTools\PX.Data\Maintenance\SM\EMailAccountMaint.cs:line 113
at PX.Data.PXLongOperation.<>c__DisplayClass17_0.b__0() in C:\Bld2\AC-FULL2019R19-JOB1\Sources\NetTools\PX.Data\Process\Operation.cs:line 1246
at PX.Data.PXLongOperation.d(Object A_0) in C:\Bld2\AC-FULL2019R19-JOB1\Sources\NetTools\PX.Data\Process\Operation.cs:line 1482
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at PX.Data.PXThreadPool.a() in C:\Bld2\AC-FULL2019R19-JOB1\Sources\NetTools\PX.Data\Process\Threadpool.cs:line 139
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()

Eventually after 30 minutes or so, the process just goes away.

Any suggestions as to what may be different between the two tenants, and/or what would cause this behavior?