docker msmtpd integration with other dockers

[lunitaris]

Hello,

I am using podman, to build a Hagrid server.
I am using https://github.com/chimbosonic/hagrid-container.

For info, docker or podman, whaterever, commands are king of the same.

container1 = hagrid server
container2= This msmtp container (will act as a SMTP relay, sending mails through a gmail account.

How do I tell another container to use the SMTP server of the msmtp container?