A Florida HOA is in breach of contract: the next step is to send a 'demand' letter seeking actionable remedy. There is a history with HOA of using email: is there any compelling reason to send the demand letter via USPS registered mail?
Why use USPS to Deliver Demand Letter when email is available
The answer essentially lies in NateEldredge's comment, and is consistent with Firefighter's Inst. for Racial Equal v. City fo St. Louis, 220 F.3d 898, 903 in that regular mail (and impliedly email) as a method of service is generally inadmissible "because the court cannot be assured that delivery has occurred".
Even if the HOA replied to your email, phoog is right in that the possibility of falsification of email records may prevent some courts from admitting service by email.