I provide a web-based service for small & local businesses and sending emails is one method of getting new customers.
However, should the first email you send them be an introductory plain text email, or a well-designed HTML email?
Supposing they both took the same amount of time to send and can be equally personalized, what is a preferable method of sending that first, introductory email?
is this list people you have been in contact with before?
Assuming that yes, then what I found worked for me best is a HTML email, but with minimal markeup. Selecting the font, maybe adding a bold ir italisized item for empahsos - but staying away from most of teh bells and whistles of the HTML email templates.
Steve's answer did hold some grain of truth, hidden in the sarcasm. Email has been deprecated a bit in the marketing realm because there's so much crap we all get in our inboxes these days that people are apt to ignore it, even if you provide some sort of incentive - like "$20 off first purchase at yourwebsite.com!" will probably just get deleted as spam. I definitely would consider alternative realms for a first contact, and ask all customers to opt-in to a newsletter if they desired to later on.
For a first, initial impression, especially for local and small businesses, consider doing more "personal" stuff - maybe chamber/commerce stuff or other networking opportunities. Or if possible, phone calls or actual visits (though they obviously are more time-consuming, they can obviously have a lot higher % rate of success than an email).
If you do send emails out, at any time, I think people by now are used to getting HTML emails. Most e-tailers I get stuff from use them, and places like Constant Contact give people a lot of options for making an HTML email that I would think a lot of their customers would use them. Just keep it simple and don't link in too many graphics.
The short answer is - both!
A well designed HTML e-mail should be better at both grabbing your recipient's attention and representing your brand. However, some people use e-mail software (or devices) which can't display HTML content. If you use the right software, you can send e-mails which 'package' both HTML and a plain text version of your content in the same e-mail. The recipient's software can then decide which version to display.
A few other things to note:
I would highly recommend using a professional e-mail marketing tool to manage your campaign, such as Campaign Monitor or Mail Chimp (there are lots of others!). These tools will help with the deliverability, making sure you are compliant with the law and will include both HTML and plain text content in your mailing.
Most importantly, they'll handle your un-subscribes and give you reporting about the number of e-mails received and how many click-throughs you've achieved.
1995 called. They want their marketing "strategy" back.
Seriously, unsolicited email is SPAM and nobody wants it. Plain text or HTML doesn't matter for spam, it all gets filtered or deleted, and is always a terrible way to introduce a service.
If you have something that genuinely adds value, hang out where your customers hang out and become a "thought leader". This'll build trust. Just spamming people will never work.