@Vero69  You could buy a day ticket for 15€ that allows you to use all regional trains, busses and some cable cars in South Tyrol. Ticket is valid on regional trains between Trento and Brenner/o and in the Vinschgerbahn and Pustertalbahn till Vierschach/Helm (border to Austria). 

Mobilcard (suedtirolmobil.info)

Im on a SAD train again today and asked directly the train staff if SAD accept Interrail and he said yes.

i am not 100% sure you may ask the Railcompany directly http://www.sad.it/de

As far as I know it is not included… unfortunately 

Correct.

Today I was on a SAD train on Pustertalbahn and they accepted an Interrail Pass of someone on the train.

Thank you for your answers. 

I did write an Email and already got the answer that interrail is not valid on their trains. 

So, I will need to buy a ticket. 

Question: Is Interrail included also on trains of SAD in South Tyrol (except Vinschgaubahn wich is not part of the Trenitalia tariff). Because they accept Trenitalia tickets (except Vinschgaubahn), and Interrail is a ticket that is accepted by Trenitalia. 

I used their trains with Interrail, but nobody checked my ticket. 

Interesting… the support of SAD wrote me explicitly a year ago that Interrail is NOT valid on their trains. Either it changed or the conductor didn’t care/had no idea of the rules (I suppose didn’t care)

I also think, they do not care. Because all other Trenitalia Tickets are valid on SAD trains (except Trenitalia Promo Pass and on SAD trains on Vinschgaubahn)

Due to someone post on Twitter, I will add the information that on Vinschgerbahn (Meran/Merano-Mals/Malles) Interrail/Eurail is not accepted.