[Dx-qsl] Mailings from within Europe to European/Russian Destinations

[Vince]

Hello Group:

I am planning to be inside Europe within a few weeks and am wondering
about rules/requirements for mailing hand carried QSLs while I am there.
In general, I will be mailing to IARU DX QSL bureau addresses.

Is there any strict requirement for air mail envelopes to be used when
mailing from Italy to other European countries or to Russia ?  I wonder
if I must use an air mail envelope obtained within Italy, for example ?
If I were mailing from here in the US, I would not bother with any
airmail envelope.

Thanks for any information.

73 and Have Fun,
de ~ Vince ~
WA2RSX   IOTA  NA-026