Hi Diego! Don't fret, it is easy to miss things in the world of DNS :-P The biggest thing jumping out at me is that your server may have already cached the DNS lookup result from your previous tests and may not be hitting the new record. What I do when setting up DKIM keys is set their TTL (Time To Live) value to 1 minute so that any cached DNS results flush out quickly. When you're sure everything is working you can increase those TTL times as well. If that fails though I recommend using mxtoolbox.com or similar tools to verify the DKIM key has been added correctly, and if all else fails engaging the DNS host's support team should help get you going in the right direction. I hope that helps!

How big is your DKIM record?? I couldnt get anything above 2048 to work...

Key size is the recommended 2048 - 

This is the point... SmarterMail reads the text record there is the option "wait for DNS verification upon enabling it... so if they are enabled... it means that the smartermail reads that record.

Due to the fact that the text record infos are generated by smartermail... is it possible that the info generated are not a correct format? Or... again it must be something very stupid. Right now I am disabling and recreating the records... with my provider as per the info generated by smartermail.

OK, I deleted the txt records from my DNS provider and now smartermail is not enabling the authentication anymore... it sounds like a bad thing but at least now Smartermail is not validating/enabling the keys. I took a picture of one of the keys enabled... just to remind that I am not crazy and they were suppoised to work before.

I also reduced the TTL to 60 sec.

I had to add a mail selector and duplicate the dkim TXT record ading the selector.

So it seems ok now.