[Samba] just some info i found, older clients and SMB..

[L.P.H. van Belle]

https://docs.microsoft.com/en-us/azure/storage/common/storage-require-secure-transfer 
 
Quote:  Connecting to an Azure File share over SMB without encryption fails 
when secure transfer is required for the storage account. 
Examples of insecure connections include those made over SMB 2.1, SMB 3.0
without encryption, or some versions of the Linux SMB client. 

I'm working this with my remote party: 
CIFS VFS: cifs_mount failed w/return code = -13
CIFS VFS: Unable to select appropiate authentication method!
I see this on older samba (4.6.x) on a wheezy server. 

Buster and recent samba works without problems. 
If you cant login for some reason with "DOM\username" 
Try username or username at REALM 


greetz, 
 
Louis