Page History

1. Cross check if you have installed the supported NAV CU as table belows

   Version	TLS 1.2 support added
   Dynamics NAV 2015	Cumulative update 43
   Dynamics NAV 2016	Cumulative update 31
   Dynamics NAV 2017	Cumulative update 18
   Dynamics NAV 2018	First release (RTM)

   
   

2. Open CustomSettings.config under server instance directory (e.g. C:\Program Files\Microsoft Dynamics NAV\100\Service\ or C:\Program Files\Microsoft Dynamics NAV\100\Service\Instances\ABC_NAV_LIVE)
3. Add/Change the following value from "SystemDefault" to "Tls12"
     <add key="SecurityProtocol" value="Tls12" />  
   
4. When save, the file must to save to somewhere else then copy back to directory

For Office 365 portal: (portal.office.com)

1. Using Office Administration: Turn on two factor authentication (2FA) for specific email account 
   (Office Portal > Admin > Users > Active users > Mulit-factor authentication > Change to Enabled > Change to Enforced)
   
2. Using email user account: Generation an app password
   (Top-right corner user icon >  View account > Security Info > + Add Sign-in method > App password > (give a name for that password) > copy that password out
   

For NAV SMTP setting:

1. Start NAV client, search "SMTP Mail Setup"
   
2. Press "Apply Office 365 Server Settings" on ribbon
3. input User ID as email address, password as App password generated last step
4. Try send email to the same email address to user ID (other email testing not working)