how to provide delay, the number of requests in one send?

Question

I'm here to ask how to provide delay and also the number of sending emails at a time in python threading. let's take an example like this I want to send emails in large quantities but on the other hand I also want to provide a maximum limit of emails in one send, and also I want to give a delay in one send let's take an example I want when the email is sent the tool will automatically delay in 5 seconds after 5 seconds then the tool will run again until so on until all emails are sent. below here I have made a delay system and the number of emails in one send, but I still doubt that when the delay is this tool is still running even though there is a delay written, and also for the system the number of emails in one send is not correct or irregular, you could say random not as expected

from inc.api3 import *
from time import sleep
import threading


clear(system_eck())  # Clean  Command
print(logo("DSWEB19778", time.asctime(), "6.0",
  "APPLE-API", "https://paypal.me/wecandoittogheter"))  # Logo COpyRights


if __name__ == "__main__":

    try:

        ask = input(genta+"    MailList #> ")
        prox = input(genta+"    ProxyList #> ")
        mod = "r+"
        op = open(ask, mod).readlines()
        listo = len(op)
        print("    Rzlt Folder Checking...")
        flr = rzlt_folder()
        if flr == True:
            print("    - Already Exist.")
        else:
            print("    - Creating Folder. Done")
            print("    List: "+red+str(listo)+"\n")

        delay = 0
        for fr in op:
        
            x = fr.strip("\n")
            delay += 1
            if delay == 25:
                sleep(10)
                print(blue+"    [+] ------------- Waiting -------------")
                delay = 0
                continue
            else:
                pass
            t = threading.Thread(target=apple_api, args=(x,prox))
            t.start()
        

    except IOError as err:
        print("    ERROR -> "+str(err))
        exit()
    except EOFError as err:
        print("    ERROR -> "+str(err))
        exit()
    except IndexError as err:
        print("    ERROR -> "+str(err))
        exit()
    except KeyError as err:
        print("    ERROR -> "+str(err))
        exit()
    except KeyboardInterrupt as err:
        print("    [KILLED] By user")
        exit()