I used Gandi's SMTP servers to relay outbound mail only (through postfix). For inbound mail, I pointed the MX record to my home IP address, where I received it

I used Gandi's SMTP servers to relay outbound mail only (through postfix). For inbound mail, I pointed the MX record to my home IP address, where I received it directly on my postfix server. This avoided my ISP's block on outbound TCP port 25, and it also gave me a reputable sending IP address economically.