eROI found that during the heaviest e-mail volume period, from 8 am to 5 pm, e-mail opening rates and CTR increased. Open rates start out at 21.4% at 8 am and rise to a high of 34.1% at 5 pm Click-through rates begin at 2.6% at 8 am and rise to a high of 6.4% at 4 pm, before falling to 5.2% at 5 pm.