If someone didn't ask to hear from you yet, it doesn't mean they won't want to hear from you later. It's your job to prove to them -- through helpful content and valuable offers -- that they should stay up to date with your company via email. If you force your email content on anyone too early, even if you know in your bones they're a great fit for your products or services, you risk preemptively losing their trust and their future business.
A web-based interface is often available to allow people to subscribe, unsubscribe, and change their preferences. However, mailing list servers existed long before the World Wide Web, so most also accept commands over email to a special email address. This allows subscribers (or those who want to be subscribers) to perform such tasks as subscribing and unsubscribing, temporarily halting the sending of messages to them, or changing available preferences - all via email. The common format for sending these commands is to send an email that contains simply the command followed by the name of the electronic mailing list the command pertains to. Examples: subscribe anylist or subscribe anylist John Doe.
Dynamic segmentation – As alluded to earlier, you can’t just send out a generic message to everyone on your list. While basic demographic data can be used to segment your list, that’s far from taking the dynamic approach. Automation tools can help you segment your list as they go through the funnel, allowing you to send personalized messaging depending on their actions and behaviors.