I have a client that has amassed a lot of their customer emails in the past year, written with a pen on paper.

I'm not completely familiar with email marketing, but am getting into it, but from what I understand, you should do a double opt-in to comply with Can-Spam laws, is that correct?

Is there a way to use one of the popular email marketing sites (Aweber, Mailchimp, ImnicaMail) and manually enter their customer's emails so that they can start sending a newsletter to them right away? Or do they have to opt in (either single or double), even though they already gave the company their email address in the past?

Thanks the for the input.

Should have been collecting numbers for text messaging marketing, would have been way better than email marketing for an offline business. If it something that wouldn't take ages to do I would email each client to sign up to my text messaging and offer them some type of incentive just to get them on board. Use something like txt180 for this purpose

Yes, it does make sense to use offline tools for a offline business. That will help your business grow faster.

You can try using aweber,mailchimp,etc but since your uploading a list your going to have to get it reviewed/checked out and most of the time if you can't prove how you got it they will deny it.

There are a few services that offer a free trial

First, you do not need a double opt-in to conform to CanSpam. All you need is permission. The double opt-in just gives an additional confirmation step that the user must jump thru in order to give you further proof that you have permission in case someone reports you as a spammer. It is added protection for you, that's all.

You should be able to make a list and simply enter the information you have and carry along with it.

If you take the list, manually load it into aweber they will require the list member to re-opt in and you will loose about 70% of your list because most people have no idea if they are on your list, and they will not re-opt in.

What I would do is create a list and mail a really good offer out to it, and have them double opt in to a new list get the gift.

Those that don't double opt in to the new list just keep on the original list and market to it. If you get a spam complaint, answer it with the truth, and you should be OK.

Email is better for offline marketing also but sms marketing is still more effective nowadays.