Yes, you need to use expressions to do it. 

To extract two email addresses from a field in a custom object using a reader and expression builder:

1. **Use the Reader**: Access the field in the custom object that contains the email addresses.

2. **Apply Expression Builder**:
   - For the first email: Use a regex or string function to extract the first email address.
   - For the second email: Apply a similar regex or string function to extract the second email address.

Example regex for extracting emails:
- First email: `(\S+@\S+\.\S+)`
- Second email: Use appropriate logic to handle the position or delimiter if the emails are separated.

I did it like this as I am not a regex expert.

substring( {{R3.passthrough}},0,indexOf({{R3.passthrough}}, ',',0)) for the first one, then

substring( {{R3.passthrough}}, indexOf( {{R3.passthrough}}, ',',0 )+2, length( {{R3.passthrough}}))

I have control over the passthrough string so I know it is always “x@y.com, z@x.com”

Thank you to everyone for replaying so swiftly.

Update, i did fall back to using the suggested regex to make it easier and work