How to send a greeting card internationally USPS?

I am sending a greeting card with a magnet in it that weighs 1.5 ounces. I plan on sending one to the UK, one to Toronto, Canada, and one to British Columbia, and one here in the US. I want to send them as First Class International Letter(except for the one in the us), and it will contain something "rigid" so it will cost a little more. Do I have to go to the post office personally to have these delivered? I'm not quite sure how to go about the process of having these greeting cards delivered, any advice would be greatly appreciated!

Just how rigid, is rigid? Thing is, without actually having your letter in my hand, I can not really make a definitive judgment. Your best bet is to take the prepared letters to your local Post Office. As you know, the one to the US will be one rate, the two to Canada another and the one to UK yet another rate.

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