You should be able to send and receive e-mails when VPN is turned On. Let us know if you use SafeConnect or McAfee VPN [Integrated with McAfee Livesafe or Total Protection] and if you have any issues in sending e-mails.
VPN came with and was installed recently with a new copy of McAfee Total Protection. I understood that Safe Connect is part of McAfee VPN so do not understand your question as to whether I use it or not.
As previously stated I can not send emails from MS Outlook when VPN is turned on. When I switch off VPN emails again go out as normal. My PC is 1 year old HP desktop and operates with Windows 10.
One of our McAfee user had the same kind of issue and it got fixed by uninstalling and reinstalling McAfee. As mentioned above, please uninstall and reinstall, it should fix the issue.
Below is another post with the same issue posted by @denj
Let us know if any further help needed.
Try to reinstall your vpn. It worked for me. Or you can change your vpn. I found the reliable one here https://veepn.com/. It doesn't cost much but provides a high level of security. I have been using it for a few months and it works well.