Well I'm ordering from a guy who lives in the UK.
What's the difference between the two?
Is it mailed from or to Ireland/N Ireland? If not, then you'd go with the british postal. The postal is different then customs in the search capabilities. Customs has xray scanners, while postal can only search mail within reason. However, with sn, there would unlikely to be a reason due to it being odorless. From what I know, customs would see the sn within the parcel from their xray. Whether or not they'd consider it medication or a toxic substance I don't know, and if they did, they'd destroy the substance. Putting your address in a list, possibly sending your a love letter (a letter notifying they seized contraband.) The issue is whether or not they'd pursue. The letter would usually just notify you're not getting your package, and to not do it again. Similar to a warning. In other words, if it's delivered via postal, the risk is very low as long as you use proper opsec, and the vender didn't mess anything up with shipping.
Difference between international and domestic is that domestic is within the country, while international is outside. The UK is sometimes confusing due to the UK being a country or sovereign state, but England, Scotland, etc are technically countries. However, all mailing within the UK is domestic. Well, Royal Mail treats N Ireland weirdly in that regard, but I digress.
Disclaimer: This is from what I've researched. You're advised to research and confirm all claims before acting upon it.
