Read Receipt Free Subscription

I am getting confused by the site it says the free edition has read Receipt and link tracking but upgrade to pro to get that. I am using the free subscription and it is working when I test it but will this feature go away over time unless I upgrade?

@Stonetown1 - The Read Receipt and Link Tracking are limited to 5 per week (I believe). If you choose to upgrade to Mailspring Pro, that limit is removed.