My friend's problem (idk how to solve it)

[Violet]

He deleted MTA then re-downloaded it and still doing the same.
Should he delete that file or what to do?

[RaMoS]

Tell him to use a VPN in case it doesn't work Tell him to restart the internet if the VPN is worked let him after two days to disconnect the VPN and run the MTA without the VPN.

[daddy]

Tell him to restart his router and open cmd as administrator then type "ipconfig /flushdns" without the quotations mark, if still having the same problem then VPN would be the only solution

[Violet]

Tell him to use a VPN in case it doesn't work Tell him to restart the internet if the VPN is worked let him after two days to disconnect the VPN and run the MTA without the VPN.

Informed him about this one

Tell him to restart his router and open cmd as administrator then type "ipconfig /flushdns" without the quotations mark, if still having the same problem then VPN would be the only solution

on it.

[Coke]

Use MTA diag and post the logs here

[Violet]

Fixed by restarting his router, Thanks to everyone who tried to help. 
@iFrank this can be locked now.