In email marketing what metrics do you use to measure the success of a campaign?

The choice of metrics here would depend upon the goals of the campaign. So, you can quote the examples of different situations. For e.g. Do you just want the receivers to join your Social Media Group or Do you want them to see a new product? In both these cases, the goals are different and so are going to be the metrics.

The commonly used metrics to measure the success of a campaign are:

i. Open Rate
ii. Click Rate
iii. Subscription Rate
iv. Reply Rate
v. Conversions
vi. CTR ( Click through Rate)
vii. Increase in website traffic
viii. Increase in referral business