Does GDPR have any effect on consent requirements or lack thereof for the sending of marketing material? I don't see why it would, but I haven't yet read it very thoroughly.
If we assume for the sake of argument that it does not, we can turn our attention to what it clearly does govern, which is the storage of personal data. In this case, the personal data are the e-mail addresses of those whom you wish to send the materials to.
You indicated in a comment that you have collected these addresses from people who have given you business cards. Surely when someone gives you a business card, that implies consent to process the data contained on the card. I can't imagine a court ruling otherwise.
There may of course be other laws that do regulate the sending of your marketing materials, as you imply in your question. You should therefore check with a lawyer to see whether anything asserted in this answer is correct, whether the prediction about future judicial findings is reasonable, and whether there are other laws that you should take into account.