docker-mailserver/docs/content/advanced/mail-fetchmail.md

To enable the fetchmail service to retrieve e-mails set the environment variable ENABLE_FETCHMAIL to 1 Your docker-compose.yml file should look like following snippet:

...
environment:
  - ENABLE_FETCHMAIL=1
...

Generate a file called fetchmail.cf and place it in the config folder.

Example IMAP configuration

poll imap.example.com with proto IMAP
	user 'username' there with
	password 'secret'
	is 'user1@domain.tld'
	here ssl

Example POP3 configuration

poll pop3.example.com with proto POP3
	user 'username' there with
	password 'secret'
	is 'user2@domain.tld'
	here options keep ssl

To debug your fetchmail.cf configuration run this command:

docker run --rm \
  -v "$(pwd)/config:/tmp/docker-mailserver" \
  -ti tvial/docker-mailserver:latest \
  sh -c "cat /etc/fetchmailrc_general /tmp/docker-mailserver/fetchmail.cf > /etc/fetchmailrc; /etc/init.d/fetchmail debug-run"

By default the fetchmail service searches very 5 minutes for new mails on your external mail accounts.