Darn you, USPS.
I used VERY visible white ink on dark paper for my save the dates. I called the USPS and I checked with 6 different post offices to make sure this was okay. They all said yes, they're legible, perfect, great.
I got news from FI's aunt that she did not receive a save the date, and she and my FMIL would like hers re-sent.
I've had to re-send several already because some addresses our parents provided to us were incorrect and we received the letters back in the mail.
But now that I'm doing some spot-checking, it looks like about 1/3 of the people we sent STDs to did not receive theirs. I did not budget to be re-making and re-sending STDs, and I honestly don't have the time to make them all again. The wedding is in 6 months.
Would it be rude to send an email saying "hey, we're so sorry your STD got lost in the mail, here are the details, please save the date and we hope that you do receive it soon!" We're already going to have to check with everyone we sent an STD to to see if they received theirs. Plus, they'll be getting their invites in four months.
I'm so frustrated! If I had gotten any sort of hint that the ink/envelope would be a problem, I would not have done it... lesson learned.