Mail-in ballots were part of a plot to deny Lincoln reelection in 1864
chron.com
chron.com
Even if a source is cited, you should remain suspicious. The source might not justify the reporting.
Even if you see video with your own eyes, you should remain suspicious. The video could be missing important context, as it was in the George Floyd case. There, the news media privately saw the bodycam video (which paints a very different picture) but continued to push a misleading account of the event.
If you trust anything from New York Times or from CNN, you should trust this too. It's at least as credible, if not more so.
It's an interesting story, because we see history repeating. The postal worker union has already endorsed a candidate. Here we see a postal worker sneaking off to destroy campaign materials: https://twitter.com/SheriffTNehls/status/1276646406682484736