Please see the following Knowledgebase for an explanation of how StoreFeeder calculates packaging sizes.
When using the Royal Mail direct integration inside StoreFeeder, you need to make sure that the packaging sizes are set correctly as the manifesting process uses the packaging size on the order to determine the correct service on OBA when manifesting.
The process is complicated slightly by the maximum depth (thickness) of Large Letter in the UK and Flats for international shipments being different.
The maximum thickness for UK Large Letters in 25mm, but the maximum thickness for International Flats is 20mm. This means that a package that has a thickness of 23mm is classed as a Large Letter in the UK but a Parcel when being sent internationally.
To overcome this, you need to ensure that your packaging sizes are correctly formatted in StoreFeeder.
There are 2 Royal Mail Packaging Sizes to cover this scenario For Large Letter products and you need to allocate the correct Large Letter packaging size:
• Large Letter/Large Letter - For all packages up to 20mm in thickness
Selecting this option will allocate Large Letter to domestic orders and Flats to International orders
• Large Letter/Parcel - For all packages between 21 and 25mm in thickness
Selecting this option will allocate Large Letter to domestic orders and Parcel to International orders
If you ship Large Letter products internationally, you will need to update your Packaging Sizes in Settings and then update the Packaging Size allocated to the appropriate products.
Go to Settings > Shipping Configuration > Packaging Sizes
To adjust your packaging sizes in the Settings, you will need to add a new Packaging Size. This will be used for products that fall between 21 and 25mm in thickness and will class as Large Letter in the UK and Parcel Internationally.
Your Packaging sizes page should now look something like above
In this example you would need to update the Packaging Size on the products that are thickness of 21-25mm as "Large Letter (21-25mm)" so that they are allocated Large Letter for UK orders and Parcel for International orders.
As a reminder, the Product Packaging Size for an individual product is set on the Additional Information tab on the Product Page.