Apple Mail is not working correctly without the use of a VPN.

You need to uninstall the VPN. Simply turning it off does not remove the process that are installed on your computer and the manufacturer of the VPN of course want you to have their service on so your web/mail traffic is routed through their servers.

Once you remove the VPN, you will find everything works correctly like it should.

Re: "Apple Mail is not working correctly without the use of a VPN".

Seems VPNs (unless supplied by an employer) are notorious for causing interference issues on Macs.

(It may be running in the background even when not "on". Using am uninstaller from its developer is best option for removal.)

Along with VPNs, other unnecessary third-party apps, eg: virus checkers,, ad blockers, cleaners, and the like are often discovered to be at the root of some quite serious interferences with the operation of Macs.

Apple support's online article

If your device has network connectivity issues, check for VPN and other third-party security software - Apple Support

Eg: says: "Third-party security software that monitors or interacts with network connections can potentially block some connections, such as those required to access the internet or communicate with other devices on your network".

fred44nl wrote:

very easy to say that I should uninstall the VPN.

but what if I do need a VPN for other reasons ??

I have to install the VPN again ??

and than uninstall when the specific connection is finished ??

The only valid reason you would have to install and use a VPN would be to create a secure point-to-point tunnel to another network. This often prevents other connections such as email or browsing outside the connected to network. If this is a valid secure connection to your workplace or other network, contact the network admin and ask them to open their security policies to allow you to access your email when connected to their network via their VPN server. I doubt they will allow your request though.

If this is a valid VPN connection required to access internal services on a private network such as email, you will need to be connected to the network through the VPN.