I tried McAffee antivirus for all of about three days before binning it.
My email client was business related, thousands of emails in it much in sub folders.
Each time I would open the email client McAffee needed to scan EVERY email and EVERY attachment in my email client, even after a system reboot it would scan everything and perhaps several times each day.
So upon a start-up or reboot and opening of email client McAffee would get to work scanning for an hour or longer before I could effectively use the PC or send/receive emails, there was no way to deprogramme this function and it wasn't clever enough to realise it had scanned such emails and/or attachments multiple times already.
Thereafter, and ever since, I went with Comodo and it's free.