Yes. The remote access features of the server and some of the security features of the server, depend on knowing the IP address of your Internet connection.  Also, to be a fully trusted email source, you must have a static IP and be able create DNS records that give details about your email server.

As a temporary work around, it may be possible for you to set up Dynamic DNS in your router/firewall or on one of your PCs. However, we do not recommend this and we do not offer technical assistance to implement this.

Most business-class DSL providers offer static IP addresses for just a few dollars per month.  This is well worth the price because it reduces the number of things that can go wrong. It simplifies access to your network and makes remote access more secure and reliable.