All of this time, we have been referring to email marketing
and NOT email advertising. There's a difference. Though the terms are very similar, advertising is actually part of the overall marketing strategy. Where marketing is the overall mix of business activity meant to bring consumer and company together for the purposes of transaction, advertising is the paid-for sponsorship and delivery of a message in a public forum. Marketing includes advertising, public relations, market research, product pricing & distribution, and even community involvement.
Your Customer Might Not See the Difference
It might be worth noting that advertising can take place in email messages, and sticklers are right to point out that email advertising is actually those annoying text prompts that come up on the sides of your web-based email host (like Gmail, for instance). But if you can accept that a radio or TV commercial is an ad because it interrupts your regular entertainment program with a pause for a commercial message, then you can see how an email marketing message that interrupts your subscribers' personal email reading process is doing the same sort of thing. It contains equal space in the subject line as any other emails they may receive that day.
But You Have Permission to Be There
The beauty of email marketing is that you aren't putting up ads in public spaces, ads on the side of Google or any other place that a potential customer might be looking for something else other than your ad. You have the permission
of your subscriber to send them asked-for information within a personal, non-public space: their inbox. If you take advantage of this trust by sending noisy, ad-riddled content, you'll soon lose this permission and get unsubscribed to.
How Your Customers Perceive You is Up to You
It's up to you to email market effectively so that you aren't perceived as blindly advertising to your subscribers. If you are selling things, of course you want to let people know about it. But the last thing you want to come across as is a used car salesman. Um, unless you are a used car salesman. But mindlessly cluttering your subscribers inboxes with bright ads that always sell the same thing is downright offensive.