Do you find it difficult to send and receive emails on your AOL email account? Did you receive an error message that reads 'Email Error 521?' The best way to fix AOL email error 521 is to run a virus scan on your system and use the Disk clean-up utility to clear any unnecessary data. If you find that the email error persists, you can call the aol email customer support phone number and ask for additional technical assistance. Professional email technicians will be able to give you advanced solutions to troubleshoot AOL email error 521.