PBGC Payment Date

Quick question regarding the PBGC payment.  I know it's due by 10/17/22 this year, my question is:

1) Does it have to be received by the PBGC by that date

or

2) Does it have to be postmarked that date

Thanks!  Have a few that waited till the last minute, so have to let them know if they have to overnight the check or just get it in the miail

There is a seven day grace period, in which they automatically wave any penalty.