We've recently been involved in looking at our Email Service Provider (ESP) partner of choice .
There are many other sources, some listed below, that have helped in the selection process by providing key areas to look at and points to consider.
And yet the best description of the number one area to focus on sprang to me as I listened to the sermon at the local church one weekend. The sermon was about how we look at the journey without the destination in mind, simply enjoying the services and facilities of the Cruise Liner we are on called Life. We have no real sense of where we are going with this and don't really know how we are progressing on that journey.
So how does this relate to selecting an ESP?
Well, my one tip would be to think about where you want to be medium and long term with your Email/Social/Mobile marketing and select your ESP accordingly. There are 100s of ESPs out there and the task of matching to your needs is difficult, especially when most of them will actually do what you want and more.
Don't be swayed by the vast amount of technology , services and consulting that is available . Be clear about where you are now and where you want to be in 6, 12, 18 months. You don't want to be in position where you have outgrown your ESP in year 1. A shelf life of 2 to 3 years is great but in some cases you may be looking to 5 years to cover the costs of the original switch.
Make sure that the fundamentals are covered before getting excited by the extra widgets available. In many cases ESPs are dumped not because they can't provide the functionality, but because the client didn't use the functionality they were paying for.
I am not advocating that you stick with one ESP for life, but then they are not just for Christmas either.
Useful Sources of Information
Email Vendor Selection
Counterpillar - Its like choosing a spouse
Be Relevant Email Marketing Blog
Chief Marketer - It's like buying a house
Email Experience Council
eConsultancy Email Marketing Buyers Guide