Hello,
I’m having a lot of problems with Mondial Relay when shipping to Italy: packages are either lost but shown as being at a pickup point, or they are returned to me without being dropped off at the pickup point…
Are you having any issues on your end? 
On my end, I have no issues with Mondial Relay Italy. I am in Corsica, so perhaps my route to Italy is shorter, but with Mondial Relay, whether it’s Italy… France… Belgium… No problems at all!! To be honest, I have more issues with Colissimo.
I recently received a returned package with the mention « oversize » written on it.
After some research, I found this information on the Mondial Relay website:
Whether you choose delivery to a Locker or a Relay Point, the weight of packages destined for Italy and Poland must not exceed 25 kg, with maximum dimensions of:
Height: 41 cm – Length: 38 cm – Width: 64 cm
It therefore seems that the maximum dimensions for packages to Italy and Poland are not the same as in France, which is not specified on Vinted at all.
I think my delivery problems stem from this.
If it can be useful to someone, I am sharing my experience.
Thank you very much for the information!