Docker Mailserver
How to configure Fetchmail with a remote IMAP server? #3994
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For the past couple decades, I have had a hosted cPanel web account that includes an email server. This has been working well -- but I have been dealing with storage capacity issues. My goal is to have docker-mailserve & fetchmail connect to the remote server, download messages and present them to clients that connect locally to dms. DMS will never be exposed to the public. I have docker-mailserve installed and fetchmail is enabled. I have a user created in docker-mailserve and have successfully sent and received a test message to and from this account. But I don't see how to specify how to connect to the remote server. I've looked through the fetchmail documentation.
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Replies: 2 comments 17 replies
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Please note that this response was created using generative AI, leveraging previously available information from the repository. This information may be helpful. However, it is our strong recommendation that you carefully consider the information before blindly applying it. To configure Fetchmail with Docker Mailserver (DMS) to connect to a remote server, download messages, and manage them locally, you need to follow these steps:
After setting up your This setup should allow you to achieve your goal of connecting to a remote IMAP server, downloading messages, and managing them locally without exposing DMS to the public. This comment was generated by Glime. |
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Unfortunately, I did that but none of the remote messages are getting downloaded. I thought I misread how to do it so I asked here. |
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I've got the polling time set to 120 seconds. But even when I send a test message to the remote server (which I can see the message is there if login via webmail -- but don't click is to avoid having it marked as read) and wait an hour or more, it doesn't show up in the local server. Here is my Here is my services:
mailserver:
image: ghcr.io/docker-mailserver/docker-mailserver:latest
container_name: mailserver
# Provide the FQDN of your mail server here (Your DNS MX record should point to this value)
hostname: docker.home.arpa
env_file: mailserver.env
# More information about the mail-server ports:
# https://docker-mailserver.github.io/docker-mailserver/latest/config/security/understanding-the-ports/
ports:
- "25:25" # SMTP (explicit TLS => STARTTLS, Authentication is DISABLED => use port 465/587 instead)
- "143:143" # IMAP4 (explicit TLS => STARTTLS)
- "465:465" # ESMTP (implicit TLS)
- "587:587" # ESMTP (explicit TLS => STARTTLS)
- "993:993" # IMAP4 (implicit TLS)
volumes:
- /mnt/docker/mailserver/data/:/var/mail/
- /mnt/docker/mailserver/state/:/var/mail-state/
- /mnt/docker/mailserver/logs/:/var/log/mail/
- /mnt/docker/mailserver/config/:/tmp/docker-mailserver/
- /etc/localtime:/etc/localtime:ro
restart: always
stop_grace_period: 1m
# Uncomment if using `ENABLE_FAIL2BAN=1`:
# cap_add:
# - NET_ADMIN
healthcheck:
test: "ss --listening --tcp | grep -P 'LISTEN.+:smtp' || exit 1"
timeout: 3s
retries: 0And Here's a screenshot taken from portainer showing the environment variables that are relevant to fetchmail:
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Local test between two DMS with fetchmailHere you go, this will let you try the feature locally with two instances of DMS. # compose.yaml
services:
dms-fetch:
image: ghcr.io/docker-mailserver/docker-mailserver:latest
hostname: mail.example.test
environment:
ENABLE_FETCHMAIL: 1
# We change this setting to 10 for quicker testing:
FETCHMAIL_POLL: 10
# Link the DNS lookup `remote.test` to resolve to the `dms-remote` container IP (for `@remote.test` address):
# This is only for this example, since no real DNS service is configured, this is a Docker internal DNS feature:
links:
- "dms-remote:remote.test"
# NOTE: Optional, You only need to publish ports if you want to verify via your own mail client.
#ports:
# - "465:465" # ESMTP (implicit TLS)
# - "993:993" # IMAP4 (implicit TLS)
# You'd normally use volumes here, for simplicity of the example, all config is contained within `compose.yaml`:
configs:
- source: dms-accounts-fetch
target: /tmp/docker-mailserver/postfix-accounts.cf
- source: fetchmail
target: /tmp/docker-mailserver/fetchmail.cf
dms-remote:
image: ghcr.io/docker-mailserver/docker-mailserver:latest
hostname: mail.remote.test
environment:
# Allows for us send a test mail easily by trusting any mail client run within this container (`swaks`):
PERMIT_DOCKER: container
# Alternatively, trust and accept any mail received from clients in same subnet of dms-fetch:
#PERMIT_DOCKER: connected-networks
configs:
- source: dms-accounts-remote
target: /tmp/docker-mailserver/postfix-accounts.cf
# Using the Docker Compose `configs.content` feature instead of volume mounting separate files.
# NOTE: This feature requires Docker Compose v2.23.1 (Nov 2023) or newer:
# https://github.com/compose-spec/compose-spec/pull/446
configs:
fetchmail:
content: |
poll 'mail.remote.test' proto imap
user '[email protected]'
pass 'secret'
is '[email protected]'
no sslcertck
# DMS requires an account to complete setup, configure one for each instance:
# NOTE: Both accounts are configured with the same password (SHA512-CRYPT hashed), `secret`.
dms-accounts-fetch:
content: |
[email protected]|{SHA512-CRYPT}$$6$$sbgFRCmQ.KWS5ryb$$EsWrlYosiadgdUOxCBHY0DQ3qFbeudDhNMqHs6jZt.8gmxUwiLVy738knqkHD4zj4amkb296HFqQ3yDq4UXt8.
dms-accounts-remote:
content: |
[email protected]|{SHA512-CRYPT}$$6$$sbgFRCmQ.KWS5ryb$$EsWrlYosiadgdUOxCBHY0DQ3qFbeudDhNMqHs6jZt.8gmxUwiLVy738knqkHD4zj4amkb296HFqQ3yDq4UXt8.$ docker compose up
# John has no mail in his inbox (Your local DMS instance with fetchmail)
$ docker compose exec -it dms-fetch doveadm mailbox status -u [email protected] messages INBOX
INBOX messages=0
# Jane has no mail in her inbox (Your remote DMS instance)
$ docker compose exec -it dms-remote doveadm mailbox status -u [email protected] messages INBOX
INBOX messages=0
# Send the remote DMS a mail internally (PERMIT_DOCKER ENV allows to send this without authentication):
$ docker compose exec -it dms-remote swaks --server localhost --from [email protected] --to [email protected]
# Jane has mail now, until fetchmail takes it:
$ docker compose exec -it dms-remote doveadm mailbox status -u [email protected] messages INBOX
INBOX messages=1
# Wait for fetchmail poll to pass, and check inboxes again,
# Fetchmail has retrieved Janes mail, deleting from her inbox, sending the copy to John's inbox:
$ docker compose exec -it dms-remote doveadm mailbox status -u [email protected] messages INBOX
INBOX messages=0
$ docker compose exec -it dms-fetch doveadm mailbox status -u [email protected] messages INBOX
INBOX messages=1Fetchmail config
You can see that it works as intended. So please refer to this example and adapt it to your remote mail server. It should successfully be able to retrieve the mail. Then adapt the example to your actual mail server setup, and it should help you troubleshoot where the problem is 👍 Looking at our docs for fetchmail config, the settings are effectively the same in the example above as they are in the docs example. I don't see anything that I can update there, beyond mentioning this more complete example for local testing/verification? Docs also provide some debug advice: https://docker-mailserver.github.io/docker-mailserver/v13.3/config/advanced/mail-fetchmail/#debugging For any additional trobleshooting, be sure to check the logs from DMS. When Fetchmail has problems connecting, it should be logging messages like this: As you can see, the connection to |
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Yes that's right! 😁 Two containers are configured, both running DMS. One is meant to represent your local DMS container with fetchmail, the other the other mail server you want fetchmail to collect from.
Fantastic! 😎 🎉 Now you can continue with the earlier guidance.
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I modified fetchmail.cf to download from my real remote mail server. The test message that I sent is no longer there. So it appears that it should be waiting for me on the local server. I don't have an email client configured to check the test account that was created locally. But since I was previously able to connect both my android phone and thunderbird on my laptop to the local server, I'm assuming that should be a simple process. Thanks for all your help! It has been greatly appreciated! |
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Yes, although in my
Thunderbird can do this, but it's probably not something I have time to walk you through (especially with my offline This is why my example commands showed you how to check a mail had arrived: # This is checking `[email protected]` account as defined in `postfix-accounts.cf`, for the example dms-fetch container:
$ docker compose exec -it dms-fetch doveadm mailbox status -u [email protected] messages INBOX
# The output from the command should look something like this:
INBOX messages=1That's an easy way to confirm the email is received locally at least, since you can see the count increase each time. There's other commands to access the actual email contents, but I don't recall what those are. The mail is stored with filenames that aren't very human friendly to identify/type 😓 If you have
Oh, if you've got separate client devices that's probably easier yes 👍 My
You're welcome! Thanks for giving DMS a go and helping to improve our documentation on fetchmail 😎 (the next release of DMS has our fetchmail docs page link to this discussion to help others troubleshoot config) |
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I added my own user account to the local server. Then I changed the fetchmail.cf configuration so that mail in the remote inbox goes to the new account. I've got thunderbird and my phone configured to get messages from the local server. The test messages are arriving! :) Oh -- and I added the necessary ports to allow email clients to connect to the local server. |
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EDIT: Seems like you deleted what I was replying to before I sent this, I take it you figured it out 😎
AFAIK that should be possible. View the current
So something like this should work as your |
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Local test between two DMS with fetchmail
Here you go, this will let you try the feature locally with two instances of DMS.