Google Analytics, and for that matter any web analytics software is very good at helping you understand important trends in your web site. What web sites are referring visitors to you, what time they are coming, what are the most frequently accessed pages and more.
BtoB Marketing writes that Using Google Analytics, e-mail marketers can gain greater control over the effectiveness and cost-efficiency of each campaign, sending carefully targeted, relevant messages.
Using Google Analytics, combined with the intelligence in your email marketing software, such as Constant Contact, Vertical Response or iContact, you can design better email campaigns with better subject lines and overall copy writing.
If you can’t measure what you are doing, continuing to do is is hard to justify.