How to serve 30 Day Notice to Vacate

[Spencer I.]

I have a wholesale deal under contract, but the property has a tenant who hasn't ever paid any rents. My agreement with the seller is to evict the tenants before closing. I know in Texas in order to file for eviction I must have proof to show the tenant received the 30 day notice. What is the best method? I would rather not deliver it in person. So would mailing a certified letter suffice, or does the tenant actually have to sign for it? (which I think is ridiculous for a few reasons)
Any advise will be greatly appreciated.
Thanks in advance
Spencer