Hello - a contact was forwarded a webcast invite email from someone we had emailed in our database. The forwarded contact is currently not in our database, but would like to be added to future webcast emails. Unfortunately, we do not have a preference center yet, so adding in the contact could potentially mean they may receive other emails as well (events, training/product updates, etc.). Although we don't send out a huge amount of emails that are event/product related, can we legally add them to the database if they are only requesting webcast emails?
No, this is illegal as you're adding the user to your mailing database without their knowledge and consent. Even if you do not have the legal consequences you could be reported to any of several Spam policing agencies. If that happens, not only could your own email service be shut down, but the email server of the company hosting your email (e.g. AOL) could be shut down. And once you're shut down, it's a long uphill climb to getting service again. You're on the list and no one wants to provide your email service.
It might be legal/illegal based on the local laws, but IMHO it is not ethical. And this might get you marked as spam.
Well, you stated "this is illegal" upfront. 😉
But I'm not sure you're seeing the whole picture. The OP expressly stated that the person did want to receive webinar-related marketing, i.e. there was express consent for at least one type of marketing - not operational - content.
That's not the same as just grabbing an email that happened to attend a webinar and starting to market to it.
Of course, we don't know whether that consent was properly processed in accordance with the jurisdiction. But if it was, it's unlikely (though not impossible) that additional marketing contact would be flatly illegal. It's going to get into what is related to the same product interest, etc. You don't have to have super-duper-finely-controlled marketing preferences if you don't want to. Ethics - and simply good marketing - are a different question!
So you do have express consent for the person to receive some kind of marketing emails from you, but you don't have consent to data storage/processing, is that your worry?
Like Steven says, talk to your lawyer. The separate consent may or may not apply - depends on where you operate and/or where the person lives.
Granular preference center control over different types of marketing (after someone is opted-in to marketing as a whole) is not mandated by any statute I've dealt with, though obviously if you present such controls you should honor them.