America’s conversation place for mineral owners
Go pick it up! It won't get better for not picking up the letter. If it's notice of something, it's effective date is most likely the date they mailed it.
If your old lease had a 2 year option to renew this may be the notification. If you are not leased, it may be a forced pooling which has to be answered within 20 days.
You need to accept the letter.
If it's an option, it probably contains a check.
Probably an option payment.