In April I sent our a couple of campaigns that I re-sent last week.
Same list minus the unsubscribes from the April sends.
The second time round the bounce rate has been much lower - about a third of the April send.
Any ideas why this may have been the case?
Hi architxt, our app automatically cleans up bounced email addresses - immediately, for hard bounces, or after 3 attempts for soft bounces. There's a good chance that quite a few invalid/abandoned email addresses have been cleaned up following your earlier campaigns, thus the reduced bounce rate.
For more information, take a look at this resource on how Campaign Monitor handles bounces.