Our company does work environment surveys, and these surveys are filled in online. All participants are sent a link to their survey in an email (personal code included).

Some of our clients have employee counts in the hundreds and sometimes in the thousands.

Our current solution is just using our SMTP-server to send this, without any form of throttling (VB6, CDO). (All recipients are usually "inside" the same domain, [email protected]) This is not a good solution, as you may imagine, this triggers every anti-spam/firewall/gatekeeper event in the clients environment. We are put in contact with their IT-department beforehand and get them to whitelist our sending server and sender-mail address.

The most usual problems we run in to are:

1. Receiving server only grabs the 20-50 first mails and rejects the rest (anti-spam measure). We sometimes can get by this by getting the it-company to whitelist us. Sometimes however, this does not work.
2. It's getting more and more normal to disable bouncing of incorrect mail addresses. This gives us no indication of whether a mail has been delivered or not. And believe it or not, most clients gives us their email list from their HR-system, not their mailsystem.

Does anyone have any suggestions for a better way to do this? We can't be the only company sending legitimate mass emails? :)