Putting a letter in the mailbox Erev Shabbos

Shabbat
1

Can I put a letter in the mail box on Erev Shabbos

See OC 247
Questions

  1. In my home letter box
  2. In my home letter box with the red Flag up
  3. In the blue boxes on the streets…
  4. At the Post Office itself

And if it is permissible in any or all the above…how close to shabbos can I place the letter in the box?

Abie Ross

2
  1. In my home letter box and in my home letter box with the red Flag up- ONLY if you know it will be picked up before shabbos
  2. In the blue boxes on the streets…YES
  3. At the Post Office itself…YES