You can ignore it, if the pools are ok. I am sending these mails if something fails when trying to set proper pools.
So the email goes to both the renter and the rig owner? Any way to tell if the problem is on our (rig) end or something the renter is doing wrong?
In most cases is due to wrong pool (missing port or something like that). I have implemented additional checks and I don't permit setting pools with no ports anymore, but some people still have saved wrong preconfigured pools.
Second most case is failed result from cgminer - yes, cgminer can sometimes fail or truncate data.
Third reason could be slow response of cgminer when connecting to new pools and if the new pool isn't connected fast enough, old pool won't be removed and mail will be sent.