I have a mobile phone GPRS connection and I want to securely use my home mail server to send mail.

I can use IMAP without a problem to read mail (username & password) but it's smtp I'm worried about.

When using the phone the IP assigned is always constant (for the purposes of this discsussion lets say its 192.168.1.2)and it seems to be the same address that everyone who uses the same phone service provider gets.

Now I could add the address 192.168.1.2 to my $mynetworks, but this would mean that I am technically an open relay for anyone who uses the same phone service as I do.

I can't use passworded smtp access, because my phone doesn't support it. I could make it more secure by checking the 'from' address and ensuring that it matches my.domain

Because I often use disposable mail addresses outgoing through that server (eg Temp_12345@not.my.domain) I only want to match the from address to my.domain when the sending IP address is 192.168.1.2

I've looked at postfix configuration till I've gone bugeyed & I can't see a way to do this.

Does anyone know how to do this, or does anyone else have a better idea for securing the mail server, but still allowing my phone access?

Steve