Why does Evolution hang each time it tries to poll my Unix Mail Spool?
Go to “Edit | Preferences | Mail Accounts | Edit | Receiving Email | Server Type” and change “Standard Unix mbox spool or directory” to “Local delivery”. Now Evolution will not hang each time it tries to poll /var/spool/mail for new emails and needs to refresh itself, and you will also have an empty /var/spool/mail as it will get fetched by Evolution automatically and transferred according to your filter rules.