The starting point, the sine qua non, of survey projects that get off the ground are adequate lists of e-mail addresses. The more people you can reach through your bulk e-mail software, the more likely your survey is to build up a sufficient participant base.

Large email lists are not always a prerequisite, because focused surveys may know their population and not need to supplement their e-mail addresses. For example, any internal survey by a law firm or law department exemplifies that. Meritas and World Services Group, both large networks of law firms, surveyed their own member firms and didn’t need a larger email list. But for most sponsors, they salivate over sources of e-mail addresses and toil to enlarge their collection.

It’s tricky, therefore, if someone dangles a desirable set of email addresses. Say a co-sponsor owns one. They probably do not want to willy-nilly hand them over to you. Those hard-won and curated addresses (including dropping bounces and unsubscribes) have significant proprietary value. This is even more true if they reveal the client base of a vendor. Nor do sponsors want to bombard invitees with irritating duplicate invitations. Still, both sponsors gain from wider outreach, so how can they share their e-mail lists and yet protect their intellectual property? Here are a few solutions.

Non-disclosure agreement: Both sides can sign matching agreements whereby they commit to use the e-mails of the other side only for specified mailings. They would not be able to use them for any other purpose or past a set date (the due date of survey responses). When companies do that, they often “salt” e-mail addresses in the list they provide so that if the covert address receives unauthorized messages, they will know that a violation has occurred and by whom.

Third party de-duplicator: Both sides might agree to send their e-mail list in a specified format to a neutral third party. That third party would identify which emails were unique to either side and which shared. This helps the parties understand the fairness of swapping emails. As a related thought, I do not know of a bulk e-mailer who maintains secure contact lists that one side or the other cannot see but that can sidestep duplicate emails, but it stands as a possible solution. The software’s reporting capabilities would also have to segregate the two lists.

Coded exchange: Instead of having a neutral intermediary match and segregate emails, the two sides might exchange coded lists of their emails. For example, each list might show only the first letter of the left side of the “at’ symbol (@) and the last two letters of the right side before the suffix, e.g., “ot.com.” This method allows the two sides to figure out which addresses are unique to one of them and which they both know. Neither side can decrypt the other side’s email list. And neither side can figure out whether the addresses are viable until they write to them.

Separate bulk emails: The parties might decide that they do not trust the other with their precious contact information nor want to share their coded lists, so each side sends out invitations and reminders from their own software. The downside of this method is that the look and feel of the invitation will change, probably, but that may not matter because you want the credibility and brand of each company to show from its aesthetics and formatting. If both use the same service, such as Constant Contact or MailChimp, they may be able to exchange templates.

In short, the terrain of swapping emails is pocked with mines. It can be done, it can be well worthwhile, but it happens with difficulty.