From a recent Sherpa meta-study:

Without question, fewer action items bring better results. One-action
emails received 55.9% clickthroughs, soundly beating two-action
emails, while newsletters with three, four or five action items were
all under 5%.

This confirms numerous MarketingSherpa studies in landing page design
that have pointed to the power of focusing an email or Web page around
a single action to avoid confusion. Segmentation and personalization
are keys to taking advantage of this principal in email.