The Apache Software Foundation

Community > Code

The ASF has a long tradition of using mailing lists as the primary communication format in projects. This is not merely because we’ve always done it that way, but is an intentional decision for the health and sustainability of our communities.

Inclusion and transparency

Mailing lists ensure that all members of the community can participate on a level field, regardless of time zone or availability, whereas synchronous communication platforms (IRC, Slack, Discord, etc.) benefit only those who are online, and in the channel, at the time of the conversation.

Mailing lists also allow archiving, so that decisions can be understood by people who were not there at the time - what was decided, why, and by whom - even years after the fact.

Synchronous communication platforms are great for end-user support, where an answer is needed quickly, and asking for clarification can be done real-time. It’s also good for social interactions, and for quick brainstorming.

But decisions, and important technical discussions, should be taken back to the mailing list so that the whole community can participate.

This is why we say, at the ASF, If it didn’t happen on the mailing list, it didn’t happen.

Mailing list etiquette

To Be Written

Mailing list configuration

Modern software development tools, including GitHub, your various ticket trackers, and CI tools, generate a lot of email. This can make your development mailing list difficult to approach for new contributors, as they appear as a wall of identical subject lines. This makes it hard for beginners to break into your project, and find out what’s going on.

Here’s some configuration tips for your mailing lists to cut through the noise and make your project’s lists more approachable and welcoming.

Infra is providing some tooling to implement the automatically sent emails. There are generally two important parts:

  1. Where should stuff be sent
  2. How should the subject lines be built up

Both these settings are done in your repositories .asf.yaml file. The full documentation of all features are documented here

Configuring where to send things

In order to configure where to send emails, please add or update the notifications section in your .asf.yaml.


This will sort of make everything go to your dev-list. Some projects have sent some of these to other lists, as the amount of emails sent from GitHub was too excessive. I will explain in the next chapter how to make this flood of emails manageable.

One thing that might be anoying, expecially for project with many third party dependencies, might be that dependabot will also be flooding your mailinglist with pretty atomic mini pull-requests.

In many projects we therefore forward dependabot emails to the commits list.

  # Send dependabot PRs to commits@ instead

Configuring the subject lines of the emails being sent

The defaults that the tooling uses seems a bit odd to me:

    new_pr: "Created: PR {repository}/#{pr_id}: {title}"
    close_pr: "Closed: PR {repository}/#{pr_id}: {title}"
    comment_pr: "Commented: PR {repository}/#{pr_id}: {title}"
    merge_pr: "Merged: PR {repository}/#{pr_id}: {title}"
    new_issue: "Created: Issue {repository} {title}"
    comment_issue: "Commented: Issue {repository} {title}"
    close_issue: "Closed: Issue {repository} {title}"
    catchall: "Updated: {repository}/#{issue_id}: {title}"
    new_discussion: "Created: Discussion {repository}: {title}"
    edit_discussion: "Edited: Discussion {repository}: {title}"
    close_discussion: "Closed: Discussion {repository}: {title}"
    close_discussion_with_comment: "Closed: Discussion with comment {repository}: {title}"
    reopen_discussion: "Reopened: Discussion {repository}: {title}"
    new_comment_discussion: "Commented: Discussion {repository}: {title}"
    edit_comment_discussion: "Edited a comment: Discussion {repository}: {title}"
    delete_comment_discussion: "Deleted a comment: Discussion {repository}: {title}"

However these result in emails that no email client I have come across is able to group to threads and I have not come acoss even one email where I got to what the email is about on my phone because all I could see was: “Commented: Discuss…”.

We therefore updated these in some projects to a lot shorter versions:

    new_pr: "[PR] {title} ({repository})"
    close_pr: "Re: [PR] {title} ({repository})"
    comment_pr: "Re: [PR] {title} ({repository})"
    merge_pr: "Re: [PR] {title} ({repository})"
    catchall: "Updated: {repository}/#{issue_id}: {title}"
    new_issue: "[I] {title} ({repository})"
    comment_issue: "Re: [I] {title} ({repository})"
    close_issue: "Re: [I] {title} ({repository})"
    catchall: "[GH] {title} ({repository})"
    new_discussion: "[D] {title} ({repository})"
    edit_discussion: "Re: [D] {title} ({repository})"
    close_discussion: "Re: [D] {title} ({repository})"
    close_discussion_with_comment: "Re: [D] {title} ({repository})"
    reopen_discussion: "Re: [D] {title} ({repository})"
    new_comment_discussion: "Re: [D] {title} ({repository})"
    edit_comment_discussion: "Re: [D] {title} ({repository})"
    delete_comment_discussion: "Re: [D] {title} ({repository})"

For some reason, the repository is required to be part of the pattern. Moving this to the end made the emails a lot more readable.


The custom templates help make the GitHub content readable on your mailinglist it will therefore not feel as overwhelming as with the defaults. Moving dependabot to the commits lists, helped reduce the content with very little information.

We would strongly encourage projects to keep as much of the discussions on their main mailingslist. If it’s a larger project and still the volumne is so high, it’s overwhelming people, think about directing some of the content to other lists.

Simply directing all GitHub content to dedicated mailing lists or lists nobody reads doesn’t help with keeping the community knowledge available. Even if it’s “on the list” someweere, it doesn’t really serve the reasoning behind the “If if didn’t happen on the list, it didn’t happen”.