I have around 4000 on my mailing list and would like to send them a message about our next event – All I want to know it I will be able to send to them all using your service? Is there any limitation to the number of subscribers I can send to at one time?

There is no maximum limit, but it should not be spam using mailing list, if we get even one spam complaint we will disconnect the account. The mails must have double option.(Subscibe and Unsubscribe)