Mailing List FAQ

What is Mailman?

Mailman is the mailing list management system in use at IMSS. It includes a web interface for performing administrative and other functions, such as subscribing and unsubscribing. Once IMSS has created a mailing list for you, you can use a web browser to set nearly all of its options, including membership, content, and moderation.

How do I create a mailing list with Mailman?

Review the IMSS Mailing Lists page. Note the information needed, then submit a requestto have the list created for you at (request type IMSS > Email & Calendar > Create a mailing list). Once the list has been created, you, as the administrator, will be notified by email. The notification email will include links to the administrative web interface (located at and to the mailing list's general information page (located at, where users can also subscribe to the mailing list. The notification email will also include other helpful notes to help you begin customizing the behavior of the mailing list.

Can I change the name of my mailing list?

You cannot change the name of the list. You can only modify the capitalization of the list. If the name must be changed, the list will need to be deleted and a new one created.

How do I begin customizing the mailing list?

From the list creation notification email, follow the link to the administrative web page. You will be prompted to log in with your administrative password, which you should have selected upon creating the mailing list. The initial administrative password should also be included in the mailing list creation notification email. Once you have logged in as the administrator, you will be allowed to modify a variety of options within several configuration categories. Links to these "Configuration Categories" are located at the top of the administrative page. Below these links will be the various options that can be changed to customize the personality of the mailing list. Most options contain a summary of what the option does and a link to a more detailed description of the option. After changing the options you wish to customize, be sure to click the "Submit Your Changes" button at the bottom of the page to confirm the changes.

How do I add/remove users to/from your Mailman list?

There are two ways to add or remove users. To begin, proceed to Configuration Categories:Membership Management->Mass Subscription/Removal (depending on your need). From here, in the "Enter one address per line below..." input box, enter one complete email address per line. If you already have a list of names in a file, you may prefer to input the path/filename in the "...or specify a file to upload" field. The formatting for both the first or second method must be one of the following formats:

One email address only per line or one name and email address per line with "" around the name and <>around the address.

Example: "Example User" <>

There is also a third way to remove people from a Mailman list. Go to Configuration Categories:Membership Management. A list of correct subscribers will be shown. To the left of each email address/name is a box in a column titled unsub. Click this button for each member that needs to be unsubscribed and click "Submit Your Changes".

How do I increase the number of users listed per page?

There is currently no way for the list administrator to change this on their own. However, if you send a request containing the list name and number of people you want per page to (request type IMSS > Email & Calendar > Mailing List Issues), we will make the change for you.

How can I export a list of all members on my list?

You cannot export a list on your own. IMSS can export the list for you in a text file. You can request this at (request type IMSS > Email & Calendar > Mailing List Issues).

How do I make my mailing list public (or moderated)?

Mailing lists on the domain can be advertised to the public (Overview of all mailing lists). By default, a new mailing list is not advertised publicly. You can change this option by following the "Privacy options" link in the administrative page's "Configuration Categories" section. You will be taken to the "Subscription rules" page. Within the page's Subscribing options, next to "Advertise this list when people ask what lists are on this machine?" , click the "Yes" radio button. In this section, you can also control the ease with which users can subscribe to and unsubscribe from the mailing list. Next to "What steps are required for subscription?", you can select how subscription requests are handled. Selecting "Confirm" causes an email to be sent to all new subscribers, from where they can confirm their subscription and be automatically placed on the mailing list. Selecting "Require approval" causes all subscription requests to await approval from an administrator or moderator before adding the subscriber to the mailing list. "Confirm and approve" is a combination of the previous two options. Additionally, in the Subscribing section, you can also require approval for unsubscription requests, although this is not recommended.

Note that advertising your mailing list as public or not requiring approval for new subscription requests may increase the chance that your list will be subscribed to and used by spammers.

How do I deal with subscribers?

List administrators and moderators are automatically notified daily of pending administrative requests (i.e. subscription requests). By default, if approval is required for subscription, an email is immediately sent to all list administrators and moderators for each subscription request. The email will contain links that will direct you to the pending moderator requests page, from which you can approve or reject the request (among other things). There is a direct link to this page from the administrative page. Click "Tend to pending moderator requests" underneath the "Other Administrative Activities" subtitle. You can change the subscription notification settings on the Configuration Categories:General Options page, in the Notifications section. If you would not like immediate notifications of each new pending subscription request, click the "No" radio button next to "Should the list moderators get immediate notice of new requests..."

My members receive a message on the first of each month with their username/password for the list. How can I stop this behavior?

This is the default behavior for Mailman lists at Caltech.

What about the mailing list's archive of posts?

Mailman has the capability of archiving all correspondence on the mailing list and allowing users to view this correspondence on their web browser. The archiving capability is turned off by default. To customize the list's archives, go to the Configuration Categories:Archiving Options page. Here, you can set whether the archiving capability is turned on or off and whether archives should be publicly or privately accessible. Privately accessible archives can only be viewed by list members when they log in.

Note that making your mailing list's archive public may increase the chance that your list and its members will be targeted by spammers.

Some of my list members are not receiving messages as they come in. What is wrong?

Digest mode is a setting that can be chosen with Mailman lists. Users can pick a size (in Kb) and messages from the list will be sent in bulk once a batch reaches that size. Along these lines, there is also a setting specifying whether these batches of messages are sent daily, regardless of whether the size is met.

How do I restrict access to specific groups of users?

There are several places within the configuration pages where access can be restricted and certain administrative decisions can be automated depending on the subscriber's (or poster's) email address, all of which are contained in the Configuration Categories:Privacy options pages. If you would like to restrict subscription access, follow the link to the Configuration Categories:Privacy options->Subscription rules page, in the Ban list section. Here, you can type in each email address that you would like to ban from subscribing to the mailing list. In addition, address lists throughout the configuration pages (including this one) also accept Python-style "regular expressions" (sometimes referred to as "regexps") to target addresses of any desired format (see Python's regular expression documentation for details). All regular expressions must be preceded with the caret ^ character. For example, if you wished to ban all potential subscribers except for those whose email addresses ended with, then you would enter:


onto a separate line in the Ban list text box. On the Configuration Categories:Privacy options->Sender filters page, in the Member filters section, there are also four text boxes where addresses and/or regular expressions can be entered to determine which action to perform when non-members send mail to the mailing list. You can configure the mailing list to automatically accept, reject, discard, or hold non-member posts for approval, all depending on the the email addresses of the sender. To set the default behavior for non-member posts, select the desired behavior from the radio buttons next to "Action to take for postings from non-members for which no explicit action is defined."

How can I stop spam and/or restrict attachments?

Your primary means of blocking spam will be to filter messages that contain specific headers. The IMSS mail server has software that flags suspected spam mail. It does so by adding a special header to the message (see the IMSS spam filtering page for more details). For the mailing list to take advantage of this spam flag, go to the Configuration Categories:Privacy options->Spam filters page. Under Anti-Spam filters, in the "Hold posts with header value matching a specified regexp" text box, type

X-Spam-Flag: YES

The value should already be entered in by default. There are two options to choose from when handling messages marked as spam. The default is to send all spam to the moderation queue for approval. This allows the administrator to scan the message to ensure that a valid message was not accidentally marked. Then those messages can be discarded without the members ever seeing them. Another choice some users opt for is to automatically delete all spam. To do this, select "Yes" for the "Discard messages with the X-Spam-Flag: YES header?". Click "Submit Your Changes" to complete this procedure. Please note that if any message is discarded using the latter method, they cannot be retrieved. If there is a chance someone may send a valid message that could be marked as spam, this option is not recommended.

If you'd also like to filter attachments (and the messages containing them), you can go to the Configuration Categories:Content filtering page, and select the "Yes" radio button beside "Should Mailman filter the content of list traffic according to the settings below?" In the first text box, you can list the MIME types of attachments that you'd like the mailing list to filter from messages. In the second text box, you can list the MIME types of attachments that are allowed by the mailing list (i.e. any attachment whose MIME type is not listed in the second text box is removed). Leaving the second text box blank allows any attachment to be sent (assuming it is not stripped by the first filter). The last option, "Action to take when a message matches the content filtering rules," determines what happens to any message that contains an illegal attachment (as defined by the two text boxes). By default, messages containing illegal attachments are discarded. If you would like these messages to be sent regardless, select the "Preserve" radio button to allow the message to be sent stripped of its attachment.