The following will help you to read the mails during 1 second, delete the mail and move on to the next one. ifIf all mails have been deleted loop will stop.
Want some more time ? changeChange sleep to 2 or more. wantWant it faster ? replaceReplace sleep 1 by a dummy command.
while (echo dq |mail) do sleep 1 ;done
while (echo dq |mail) do sleep 1 ;done