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Mailing List Etiquette

Across most open source projects a very specific email posting style is used. This is an attempt to document the main points of that style.


Some higher-volume mailing lists recommend prefixing subject lines with topic tags in square brackets, to make threads easier for readers to quickly categorize and decide what they should read. For instance, if you are sending to openstack-discuss and you want to talk about future development work on nova, your subject could be [dev][nova] Nova should be renamed Avon instead!.

For the openstack-discuss list in particular, see the OpenStack Project Team Guide chapter on Open Community where its extensive use of topic tags is documented.


Plain Text

Please don't send HTML email. Send your email as plain text only. You really don't need any fancy formatting that HTML allows. Also, HTML email will screw up the formatting of any code you quote in your email.

If you do send HTML email (please don't), at least configure your client to include a plain text alternative as an attachment.

Line Wrapping

Lines should be wrapped at 72 characters or fewer. That is, in the plain text email you send, every line will contain a carriage return character in the 72nd column or before.

The exception to this is quoted text - the quoted text does not need to be line wrapped, especially if you are quoting someone's patch in your reply. Wrapping quoted prose is acceptable for improved readability as long as its meaning is not lost in the process.


We use the interleaved style of replies. You place your replies to specific points directly under those points in the quoted text.

> Red is my favorite color.

Red sucks.

> But yellow is nice sometimes.

I agree. Yellow is nice.

Reply Level Indication

When quoting previous emails in our replies, we use > to differentiate the quoted text from our email. You can have multiple levels of replies indented like this.

> > > Red is my favorite color.
> > 
> > Red sucks.
> Does not!

Does too!

Attribution Lines

Quoted text should also be preceeded by an attribution line.

Bob wrote:
> Jim wrote:
> > Bob wrote:
> > > Red is my favorite color.
> > 
> > Red sucks.
> Does not!

Does too!

This is important because if someone gets cc-ed on a conversation and is missing the context, the attribution lines help them make sense of the conversation so far.


You don't need to quote all of an email in order to respond to one specific point. Rather than doing:

> Red is my favorite color.

Red sucks!

> But yellow is nice sometimes.
> I have a lot of opinions on colors.

you should trim the parts of the quoted email that aren't relevant to your contribution. So, this would be sufficient:

> Red is my favorite color.

Red sucks!

Also, it is okay to reformat the original email slightly when trimming. Rather than:

> Red is my favorite color. But yellow is nice sometimes. I have a

Yellow rocks!

it's better to do:

> But yellow is nice sometimes.

Yellow rocks!

However, don't go overboard with trimming. Retain any context that might be useful to people joining the thread later.


Email clients insert a Message-ID: header and when you reply to an email, that email's ID will be included in the In-Reply-To: header of your response. This allows email clients to display the thread like this:

From    Subject            Date
Joe     Pizza!             13.00
Ray       Re: Pizza!       13.25
Sue       Re: Pizza!       13.15
Bob     Colors             12.02
Jim       Re: Colors       13.05
Bob         Re: Colors     13.10
Mary      Re: Colors       12.30

See also this nice example of a mailing list thread.

Many folks who deal with a lot of email rely heavily on threading like this. For example, they can quickly glance at a thread and mark all the emails in the thread as read.

Things get annoying when people either use a mail client that does not handle threading correctly or hijack a thread for a completely different subject. So, instead, you might get:

From    Subject            Date
Bob     Colors             12.02
Joe       Pizza!           13.20
Ray         Re: Pizza!     13.25
Jim       Re: Colors       13.05
Mary      Re: Colors       12.30
Sue     Re: Pizza!         13.15
Bob     Re: Colors         13.10

What happened here is that Joe hijacked the Colors thread with his Pizza! email and both Bob and Sue are using mail clients that don't thread correctly.

This drives people crazy! Please make sure you avoid both problems.

Changing Subject

Sometimes it is appropriate to change the subject of a thread rather than starting a new thread. For example, you my want to drill down into a subset of subject of the original thread. One convention for doing this is:

From    Subject                        Date
Bob     Colors                         12.02
Jim       Red (was Re: Colors)         13.05
Bob         Re: Red (was Re: Colors)   13.10
Mary      Re: Colors                   12.30


The threading section above dips into a topic known as 'netiquette'. For example, it is considered bad form (i.e. bad etiquette) to hijack a thread, or to format your emails in some strange way.

This is a large topic, but let's try and cover the most important and relevant items.

Avoid cross-posting

Cross-posting is the action of posting the same message to several mailing-lists at the same time. While it may sound like a great way to reach a wider audience, it creates problems with replies, as not everyone will be able to post their reply back to every mailing-list you posted to. This results in cross-hatched threads, where some replies are missing depending on the mailing-list you're trying to follow the discussion to.

Alternate solutions include choosing a main mailing-list for your message and posting separate pointers to that discussion on other mailing-lists, asking to reply to the thread there if interested. Or post separate messages on each mailing-list, to create separate threads.

Keep Discussions On-List

When replying to a discussion, or starting a new discussion, your instinct should be to have that discussion on the appropriate mailing list.

Avoid taking a discussion off-list, making sure you reply to the mailing list rather than directly to discussion participants.

Avoid starting a discussion off-list. If you find yourself Cc-ing more than 2 or 3 people, you should probably just send to a mailing list instead.

Avoid Cc-ing additional addresses when posting to a mailing list, since this can lead to split discussions among non-subscribers and duplicate deliveries for list subscribers. Refer interested individuals to the published list archive, if they would like to follow a discussion without subscribing.

We use mailing lists because it gives a wider audience the opportunity to stay involved or informed, it encourages openness and it means the discussion is archived for future reference.

Yes, sometimes it's not appropriate to discuss something on a mailing list. But this should be the exception, not the rule.

Many of our mailing lists avoid altering the original From and Reply-To headers of messages sent to them, but all still provide RFC 2369 List-* headers so using a mailreader with reply-to-list functionality is strongly recommended. If you're unfortunate enough not to be using such a client, you may be able to get away with using reply-to-all and then removing any irrelevant addresses (making sure to still include the mailing list's posting address).

Job postings

OpenStack-related job postings should be posted to the (free) OpenStack job board, not the mailing lists.

Reviews request

Please don't send review request directly on the mailing list but use other channels like direct email or IRC ping, see Thierry's email on this :

Core reviewers already receive emails about things they should review, and use tools to prioritize their review queue. If you'd like someone in particular to review things, send an email to them or ping them on IRC. If you'd like to get your review prioritized up, chiming in in the corresponding weekly team meeting should be a hundred times more efficient. But sending something which duplicates the automatic email notification is ineffective and creates ML noise (which is a pain for everyone).

Instructions For Specific Clients

The kernel's Documentation/email-clients.txt is pretty comprehensive.


To use 'Plain text mode':

  1. Click COMPOSE in your Gmail's left navigation bar (You can also press 'c' if keyboard shortcuts are enabled)
  2. Click the 'More options' downward pointing triangle in the email composition pop-up
  3. Make sure 'Plain text mode' is checked.
  4. If 'Plain text mode' does not have a checkmark before it in the menu, click it. (Otherwise, click anywhere in the email's body text to close the 'More options' menu.)
  5. This setting is persistent, so new emails you compose will also be in 'Plain text mode'. However, if you (for a specific email) set back to 'HTML mode' (this happens automatically if you use some formatting options), that will also be persistent. So, if you send a one off HTML mail, you'll need to remember to go back into 'Plain text mode' following that.

Note also that gmail wraps plain text messages at 78 characters, but it does not make this wrapping visible in the composer.


Don't use it!

Alternatively, try this QuoteFix Macro.


It looks like the Zimbra email composer just can't handle these guidelines.

You can get close with "When replying to an email: Include original message" and "use prefix >", but it's still not good enough. Even with those settings, Zimbra doesn't allow you do nice attribution lines and it line-wraps quoted text.

Honestly, it looks like a lost cause. Use a proper email client like Thunderbird for most of your work.


To configure it to send plain-text email, go to Accounts, Composition & Addressing and uncheck "Compose messages in HTML format".

You should also disable text/plain; format=flowed or you'll see line wrapping issues. Go to Preferences, Advanced, Config Editor and disable mailnews.send_plaintext_flowed. Update: this setting seems to be disabled by default in recent versions of Thunderbird. It's still best to double check!

Or you can just install the Asalted Patches add-on. "Stops your patches from being assaulted".


To configure it to send plain-text email, go to Preferences, Composer Preferences and unset "Format messages in HTML". Also, set reply style to "Quoted". In Mail Preferences, set Plain Text Mode to Prefer PLAIN.


Rumour has it that it "just works fine by default". HTML formatting can be enabled globally or per recipeint. Line wrap can be customized in "Configure Kmail > Composer > General"


Is this still common? I dunno, but it should work fine.

Apparently it's a good idea to set the "quell-flowed-text" feature.


If you're using mutt, you probably know all this already. It basically does most of the things recommended here by default, and you'll probably find the reply-to-list (L in the default keybinding) feature especially useful.


  1. Wikipedia
  3. Fedora guidelines
  4. OpenSUSE guidelines
  5. Instructions for configuring git send-email on Windows
  6. SubmittingPatches
  7. email-clients.txt
  8. An example of a mailing list thread.