In case so required, change of phone number may be requested. Does not allow access with RDSI line at 128 kbps. Does not allow access outside of Costa Rica using roaming facilities via iPass. They are concerned about many people using the same account. Thus the 1 single simultaneous requirement.
Email is completely different than internet access.
I have never heard of any ISP not letting you check email on their servers if you connect from a different service provider. Nobody wants to be associated with spam, so SMTP accounts are strictly controlled. Almost every ISP restricts use of SMTP servers to only people connecting using their service. So if you want to send mail you usually have to use the local ISP's smtp servers or something like hotmail. Hope that answers your questions.