If your ISP will not allow you to relay through them, there are companies that provide email relay services.  One is Tzolkin (https://www.tzo.com/cgi-bin/Orders.cgi?sku=OMR).  We have used them in the past for their Dynamic DNS service and they were very reliable.  They have different usage levels; under $50 (US) a year, for 2000 messages per month.  Hope this helps.

Hi,

 My ISP blocks Port 25, is there anyway I can still use Mercury SMTP to send out mail? ....for example using a different DNS server that is not from my provider? how would I do this?...just throw an address into the "Name Servers" in the MercuryE config?

 Thanks for any suggestions,
Andrew

If port 25 is blocked for outgoing traffic it won't help with any DNS fixing. Your options are to contact your ISP, inform them that you will be running a mail server and ask them to open port 25 for you (which reasonably serious ISPs probably will do), or use MercuryC instead of MercuryE and relay outgoing mail though your ISP's SMTP server.

/Rolf