I see, this is not going to work for me
The spammers can not be underestimated
So there would be nothing easier for them then remove the "+3" from the e-mail "firstname.lastname@example.org" and instead of that email going to specific folder it would get delivered to Inbox and I would not be able to track who sold/abused that unique e-mail alias "email@example.com" address that we all create for every website that wants e-mail registration ...
3 - is unique number that would identify specific user (1 for donald, 2 for ivanka, 3 for tiffany etc. for eg.)
snap.pack - would be the name of the server that e-mail has been used to register with
20170101 - Is the date that it has been registered with the website
That way, this alias would be unique and easily traceable to whom abused that specific address.
I have listened to program on BBC Radio 4 while ago and someone there was talking about this approach (and making money back from companies that send spam to him), he used same approach, but without the unique date and the spamming company argued that the email was not unique etc. ... so when he start making the aliases unique spam went down to 0 and same has worked for me in the past when running the mail and manually adding aliases to /etc/postfix/virtual on server set up from article over here
So it looks like there is not way to get emails starting with "prefix number dot something dot dateandtime at domain.name" be delivered to predefined user without having to add them manually via Mail -> Aliases menu