Same offer; different subject lines. Test the exact same e-mail
promotion in the exact same format and change only line of each.

Same subject line; different letters. Use the same subject line
And the same format , but alter the body of your letter sligthtly.
This doesn't mean you have to write an entirely new letter; instead,
try tweaking just one section so you can determine which
change makes the difference.

Different opening paragraphs. It's a good idea to create a letter
that works , then try a couple of different opening paragraphs.
This is area of the letter that will have the biggest impact on your sales,
because this is where people make their "read it or delete it" decision.

Different offers. You don't always have to be testing the effec
of different salescopy – you can also try testing the appeal of o
offer versus the interest in another.

Different price points. You should always test a few different prices
for a new product or promotion. It's amazing but true – a product
will often sell more at a higher price then at a lower , discounted
price…though often somewhere in between is your best bet.
Test at least three prices points for any product.

Different angles. Try a couple of different angles in your promotions.

Different salesletters. If your e-mail promotions link your customers
to a salesletter at your web site, try using the same mailing and the
same subject line, but linking to different salesletters or web pag
( with different headlines, angles, etc)

Different formats. While we used to send almost all of our e-mail
promotions in HTML format , we have recently discovered that our
audience is more responsive to mailings in plain text format. Again,
if we weren't constantly testing and tweaking our promotions , we
never would have learned this.

Short copy versus long copy. Depending on your promotion , the
length of your e-mail can play a large in its success.
Typically , e-mail that are more than two pages in length don't get
read – but this is not always the case. Sometimes , you need tha
extra, persuasive text to convince your potential customers that your
offer really is the best. Try testing a three-quarter-page email
promotion versus one that is closer to one and half pages in length.

The single most important thing you can do to guarantee the long term
success of you e-mail marketing program is to constantly test every
aspect of your promotions.

So what , exactly , should you be testing? Anything and everything.
You should try testing things like:

Subject lines
Offers
Opening paragraphs
Price points
Angles
Salesletter
Formats

..and this is just the beginning. Fell free to test as many
different elements of your e-mail promotions
as you can think of. It can only improve your bottom line.