I am constantly getting "535 Authentication Failed" but the username/password supplied is correct. Config/Log below. Two-factor auth is disabled. Any ideas what could be wrong?

Config

1. #
2. # Config file for sSMTP sendmail
3. #
4. # The person who gets all mail for userids < 1000
5. # Make this empty to disable rewriting.
6. root=response@pracevdigitalu.cz
7. 
   
8. # The place where the mail goes. The actual machine name is required no
9. # MX records are consulted. Commonly mailhosts are named mail.domain.com
10. mailhub=smtp.zoho.com:587
11. 
    
12. # Where will the mail seem to come from?
13. rewriteDomain=pracevdigitalu.cz
14. 
    
15. # The full hostname
16. hostname=ssmtp.pracevdigitalu.cz
17. 
    
18. # Are users allowed to set their own From: address?
19. # YES - Allow the user to specify their own From: address
20. # NO - Use the system generated From: address
21. FromLineOverride=yes
22. 
    
23. # Use SSL/TLS before starting negotiation
24. #UseTLS=Yes
25. UseSTARTTLS=Yes
26. 
    
27. # Username/Password
28. AuthUser=response@pracevdigitalu.cz
29. AuthPass=<omit>
30. Debug=YES

1. sSMTP[10114]: Set MailHub="smtp.zoho.com"
2. sSMTP[10114]: via SMTP Port Number="587"
3. sSMTP[10114]: Creating SSL connection to host
4. sSMTP[10114]: 220 mx.zohomail.com SMTP Server ready September 11, 2018 2:45:40 PM PDT
5. sSMTP[10114]: EHLO ssmtp.pracevdigitalu.cz
6. sSMTP[10114]: 250 SIZE 53477376
7. sSMTP[10114]: STARTTLS
8. sSMTP[10114]: 220 Ready to start TLS.
9. sSMTP[10114]: SSL connection using ECDHE_RSA_AES_256_CBC_SHA1
10. sSMTP[10114]: EHLO ssmtp.pracevdigitalu.cz
11. sSMTP[10114]: 250 SIZE 53477376
12. sSMTP[10114]: AUTH LOGIN
13. sSMTP[10114]: 334 VXNlcm5hbWU6
14. sSMTP[10114]: cmVzcG9uc2VAcHJhY2V2ZGlnaXRhbHUuY3o=
15. sSMTP[10114]: 334 UGFzc3dvcmQ6
16. sSMTP[10114]: <omit>
17. sSMTP[10114]: 535 Authentication Failed
18. sSMTP[10114]: Authorization failed (535 Authentication Failed)

Thanks,

Tomas