Cap of unidentified organisation

[Fritz]

Can anyone identify this cap. Named to SS-Untersturmführer Mix, 3./SS-Verfügungstruppe ???
He may have been a member of this other organisation, and at the same time, SS-VT.
Material appears to be very dark blue velvet, red piping, eagle as per Reichspost,
Peak is SS marked.

 

[Eddieq]

I would have definitely said postal. Could the ss mark be a later addition?

[Eddieq]

Here is another postal officers cap- no runes though.

[Fritz]

I thought at first postal, but the Reichspost had orange piping, and normally a different cockade as below