I would go on line in make a complaint. The Post Office will be required to follow up with you regarding the matter. All carriers are required to stop at my boxes with flags up whether they have mail for them or not. They have changed a few route times so the time of day they are passing your box your flag may not be visible. Flags that are not the same color of the mail box, bright red, yellow and etc are easier to see.
It is possible that with the currently high volume right now that your carrier may possibly not stop if they don't have incoming mail to deliver to you. I had this happen recently. My carrier did not pick up my outgoing letter for a couple days, until I had incoming mail. If you have a deadline, may be prudent to drop it at the post office.
Thank you... I will make sure I drop off my outgoing mail at the post office during peak time.
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