Yes, all accounts are subject to limits on sending mail, to prevent abuse of our servers by spammers. The default limits are as follows:
A recipient is any email address listed in the To, Cc or Bcc headers of the email, or specified via SMTP commands.
While the default limits are ample for most users, we realize that some of our customers might have a legitimate requirement to send to a larger number of recipients per message than the default limits permit. As long as your use of our SMTP servers complies with our acceptable use policy (essentially: no spam) we can raise the per-message recipient limit for your account, on request.
There are no limits for receiving mail, other than your mailbox size.