Welcome emails series

Hello Pablo and thank you for posting!

You can schedule newsletters, based on the days after subscription. In the Sending Details tab of the newsletter sidebar, you can set the "Scheduled sending" to "Campaign after Subscription".
After selecting that option, some inputs will appear to allow you to set the days after subscription for this campaign newsletter.

As always, you can select specific mailing lists to receive this campaign.
Please note that you must have a cron job key for all scheduling options to work.

Thanks again!

I understand what you mean now.
At the moment this is not possible.

In order to achieve this, we would have to somehow exclude them from all other newsletters for an unknown amount of time (since you may have an indefinite amount of welcome emails) and to switch this flag after some time.
Keeping them out of the normal mailing lists would complicate things like editing their lists from the Edit Lists layout.
The simplest way I can think of would be to add an option somewhere to define whether you want subscribers to receive normal newsletters during onboarding or not.
NS Pro would then have to find the latest onboarding newsletter, get its "days after subscription" value and exclude all subscribers from normal newsletters that subscribed less than this time.
It affects NS Pro both in the sending process and the recipient calculation process, so it's quite a large change.

If you have any suggestions, please feel free to make them.

I think having temporary-transitional lists is a nice way to onboard someone. Nice idea!
Introducing tags is a completely different feature, and I don't really think that could work.

So, perhaps we could go with transitional mailing lists. Would you like to write this down in our possible features roadmap or would you be interested for our feature implementation on-demand service?
If you would like to implement this now, feel free to contact me at me@mavrosxristoforos.com.

Thanks again!