Hi - Thanks for your question. In general, you want the mailing to get through to your audience of business decision makers whose mail is often filtered by a "gatekeeper" - an assistant, the mailroom, etc. It used to be that business-to-business marketers would use a very businesslike #10 close-faced white envelope, letter, and brochure or go for impact with a 3D mailing in order to get through. However, the most common formats being used today in business-to-business mailings according to recent articles are postcards and self-mailers. And they seem to be getting good ROI. For postcards, larger sizes are recommended as they stand out in the mail better than small sizes. So, you could start there, use either the postcard or self-mailer format, and leverage what large companies who mail large quantities and do lots of tests have learned.
Is the mailer going out to the same list(s) every 2 months? If so, I wouldn't mail the same piece over and over. People will get too used to it, plus those who didn't react might respond to a different approach, assuming your list is well-targeted to those who would have interest. So, I would create a campaign of 3 or 4 cards with different messaging and different creative, but with a family or branded look. You want people to notice the cards and who they are from, but by using a campaign approach, you can hit different "pain points" and so have a greater chance of connecting. Make all the messages strong, so they also tell your full "story" for those in your audience who might remember them all.
Response is highly dependent on your offer and the length of the sales cycle. Take a look at the ROI Estimator on the home page of our site. You can use it to play with different response and cost scenarios and expectations.
If you can, you should do some testing to see what resonates best with your target market. You could use the same design and test 2 different headlines in one mail cycle. This is called an A/B split test. I suggest testing headlines as many people read only the headline to make their decision whether to pay any attention to what you have to say. And you could test 2 different offers in another mail cycle. I suggest testing offers as the offer is also a key leverage point. However, test only one thing at a time and test only if you have a large enough list to create a large enough test group where you have some confidence in the comparative results. If you are mailing to only several hundred names total, just go with your one best effort.
Good luck and let us know how it goes. I'd be happy to answer any further questions you have. Just drop me a line.
Best regards,
Sandra