Actually there are a number of issues that would make this a heavy lift.toggle quoted messageShow quoted text
First off, squirrelmail uses php 5 and is not Stretch friendly. Also, that email client is now poorly supported. PiGate 1.5 currently does not run on the new RPI 3 B+. There are some recent issues with changes made by the WDT that Mark Griffith has been working on, but you would have to contact him for current status.
Not to be negative as I very much like PiGate and respect the hard work Mark has put into that project. If fact, I’ve built several over the past couple years. Just noting that it may be a more complex undertaking than seen at first “blush”. :)