Can you help me to read and understand what is the cause of these errors in the administrative log?

[2020.04.19] 11:41:40.805 TlRMTVNTUAADAAAAGAAYAEAAAAAAAAAAWAAAAB4AHgBYAAAALAAsAHYAAAAAAAAAogAAAAAAAACiAAAABYIAALmHV3KDgqxl4rTUP4WJ6AMpRrHxc7jxdVcASQBOAC0AOABIAEMAOABPAEUAVABMADYARQBUAGkAbgBmAG8AQABwAHIAbwBzAGUAYwBjAG8AYwByAG8AcwBlAHQALgBpAHQA Lunghezza della matrice di destinazione insufficiente. Controllare destIndex, la lunghezza e i limiti inferiori della matrice. [2020.04.19]    in System.Array.Copy(Array sourceArray, Int32 sourceIndex, Array destinationArray, Int32 destinationIndex, Int32 length, Boolean reliable) [2020.04.19]    in MailService.Protocols.Authentication.LmVersion1Response.ValidateHash(String password, String digest, String domainName, String& failure, List`1& logLines, Boolean removeFromCache, Boolean removeFromCacheOnFailure) [2020.04.19]    in MailService.Protocols.Authentication.AuthenticateMessage.TryParse(Byte[] data, String hostname, String& failure, List`1& logLines, Boolean removeFromCache) [2020.04.19]    in MailService.Protocols.Authentication.NegotiateMessages.Parse(Byte[] data, String& response, String base64, String ip, String hostname, ProtocolTypes types, Boolean removeFromCache) [2020.04.19]    in MailService.Protocols.Authentication.AuthenticationManager.Parse(String base64, String ip, String hostname, ProtocolTypes types, Boolean removeFromCache) 11:41:40.852 [2020.04.19] [87.21.247.31] POP Only NTLM is supported - Hostname: , ProtocolType: POP, Message: [AUTH NTLM] 11:41:40.899 [2020.04.19] AUTH PLAIN Lunghezza non valida per una stringa o una matrice di caratteri Base 64.    in System.Convert.FromBase64_Decode(Char* startInputPtr, Int32 inputLength, Byte* startDestPtr, Int32 destLength) [2020.04.19]    in System.Convert.FromBase64CharPtr(Char* inputPtr, Int32 inputLength) [2020.04.19]    in System.Convert.FromBase64String(String s) [2020.04.19]    in MailService.Protocols.Authentication.AuthenticationManager.Parse(String base64, String ip, String hostname, ProtocolTypes types, Boolean removeFromCache) [2020.04.19] 11:41:40.931 AUTH PLAIN Lunghezza non valida per una stringa o una matrice di caratteri Base 64. [2020.04.19]    in System.Convert.FromBase64_Decode(Char* startInputPtr, Int32 inputLength, Byte* startDestPtr, Int32 destLength) [2020.04.19]    in System.Convert.FromBase64CharPtr(Char* inputPtr, Int32 inputLength) [2020.04.19]    in System.Convert.FromBase64String(String s) [2020.04.19]    in MailService.Protocols.Authentication.AuthenticationManager.Parse(String base64, String ip, String hostname, ProtocolTypes types, Boolean removeFromCache) 11:41:40.962 [2020.04.19] APOP info@proseccocroset.it 4bd339e8dbca4188bae793d39f1aa31d L'input non è una stringa Base 64 valida poiché contiene un carattere non Base 64, più di due caratteri di riempimento oppure un carattere non corretto tra i caratteri di riempimento.     in System.Convert.FromBase64_Decode(Char* startInputPtr, Int32 inputLength, Byte* startDestPtr, Int32 destLength) [2020.04.19]    in System.Convert.FromBase64CharPtr(Char* inputPtr, Int32 inputLength) [2020.04.19]    in System.Convert.FromBase64String(String s) [2020.04.19]    in MailService.Protocols.Authentication.AuthenticationManager.Parse(String base64, String ip, String hostname, ProtocolTypes types, Boolean removeFromCache) [2020.04.19] 11:41:41.008 USER info@proseccocroset.it L'input non è una stringa Base 64 valida poiché contiene un carattere non Base 64, più di due caratteri di riempimento oppure un carattere non corretto tra i caratteri di riempimento. [2020.04.19]    in System.Convert.FromBase64_Decode(Char* startInputPtr, Int32 inputLength, Byte* startDestPtr, Int32 destLength) [2020.04.19]    in System.Convert.FromBase64CharPtr(Char* inputPtr, Int32 inputLength) [2020.04.19]    in System.Convert.FromBase64String(String s) [2020.04.19]    in MailService.Protocols.Authentication.AuthenticationManager.Parse(String base64, String ip, String hostname, ProtocolTypes types, Boolean removeFromCache) 11:41:41.040 [2020.04.19] [87.21.247.31] POP Only NTLM is supported - Hostname: , ProtocolType: POP, Message: [QUIT]