Installing and configuring vpopmail

March 17, 2022 Roberto Puzzanghera 81 comments

Vpopmail provides an easy way to manage virtual email domains and non /etc/passwd email accounts on your mail servers.

The purpose of this note is to show how to use Mysql as the authentication system. Having a users database also offers the advantage of communicating with the database via PHP, and creating web-based user interfaces to manage accounts.

Patch details

The patch we'll apply is the result of the following bunch of patches:

  • sql-aliasdomains patch, which makes vpopmail save the aliasdomains to MySQL. This makes the dovecot sql auth driver aware of the aliasdomains, provided that you modify the sql query as well (see the dovecot page for more info).
  • defaultdelivery patch, which makes vpopmail to copy your favourite delivery agent (stored in QMAILDIR/control/defauldelivery) into the .qmail-default file of any newly created domain, overriding the default vpopmail's behaviour, where vpopmail copies its delivery agent vdelivermail. You have to configure with --enable-defaultdelivery to enable this.
    If the functionality is disabled (--disable-defaultdelivery, which is the default option) vdelivermail is installed with the "delete" option instead of "bounce-no-mailbox", which is not reasonable anymore.
  • dovecot-pwd_query patch
    If you want to use the dovecot's sql auth driver with one table for each domain (--disable-many-domains) you have to heavily customize your password query. With this patch vpopmail installs the sql procedure and functions in the database when you create a new domain. The procedure can be called by dovecot to perform the auth.
    The sql stuff supports aliasdomains and mysql limits and will be loaded from ~/vpopmail/etc/pwd-query_disable-many-domains.sql. You can customize the sql procedure editing this file.
    You have to configure with --enable-mysql-bin=PATH as we have to install the procedure calling the mysql bin as a shell command (no way to load an sql query from a file in C language, comments welcome).
  • vusaged configure patch
    It seems that at least on Debian 11 vusaged refuses to run the configure successfully, as the mysql libraries are not linked (configure: error: No vauth_getpw in libvpopmail). After some inspection, I noticed that avoiding the break of the configure command, the following make command will find libmysqlclient and compile with no problems, and the program works as expected.
    NB: an autoreconf -f -i into the vusaged directory is needed before configuring, as the configure.ac script was modified.
  • recipient check patch. It can be used with Erwin Hoffmann's s/qmail to accomplish the recipient check. Not important in my installation, look at doc/README.vrcptcheck for more info.
  • gcc-10-compat patch, which gets vpopmail to compile with gcc-10

Denying bad DNS HELO/EHLOs

February 26, 2022 Roberto Puzzanghera 0 comments

The RFC-821 Section 3.5 states that 

The sender-SMTP MUST ensure that the <domain> parameter in a HELO command is a valid principal host domain name for the client host. As a result, the receiver-SMTP will not have to perform MX resolution on this name in order to validate the HELO parameter.

The HELO receiver MAY verify that the HELO parameter really corresponds to the IP address of the sender. However, the receiver MUST NOT refuse to accept a message, even if the sender's HELO command fails verification.

Not denying clients with a bad HELO/EHLO DNS can be also considered a wise thing, just not to update too frequently our whitelist for those clients who don't set up their DNS properly.

On the other hand, it is a matter of fact that most spammers use fake domains -very often our own domains-, or even random strings or not solving domains, as their HELO/EHLOs.

For example, consider the following log lines (I have plenty of them in my logs):

2022-02-01 10:19:53.142643500 helo-dns-check: HELO [yq3H9cDKgS] from [109.237.103.41] doesn't solve
2022-02-01 09:53:05.772497500 helo-dns-check: HELO [sagredo.eu] is a local domain but IP [183.240.55.119] is not a RELAYCLIENT

I think that at least such kind of failures should be blocked. I'll explain below how to set up a filter which deny clients with these particular DNS failures:

  1. not solving HELO/EHLOs, i.e. random strings or domains with no A record at all.
  2. fake HELO/EHLOs containing one of our domains, when the DNS doesn't solve to one of our IPs and RELAYCLIENT is not defined;
  3. clients whose A record doesn't match the domain in their HELO/EHLO. This is completely against RFC-821, so my configuration will not refuse these connections, just log them.

Greylisting for qmail

February 11, 2022 Roberto Puzzanghera 7 comments

Greylisting is a method of defending e-mail users against spam. A mail transfer agent (MTA) using greylisting will "temporarily reject" any email from a sender it does not recognize. If the mail is legitimate, the originating server will try again after a delay, and if sufficient time has elapsed, the email will be accepted.

While greylisting is not effective as in the past, it still cut a certain fraction of the total spam.

qmail-spp greylisting plugin

I introduce here how greylisting can be implemented on qmail by means of another qmail-spp plugin, which saves the data in MySQL. Having the data in MySQL is useful to measure how much spam is blocked by greylisting.

  • More info here
  • Author: Manuel Mausz

Dovecot vpopmail-auth driver removal. Migrating to the SQL driver

March 9, 2021 Roberto Puzzanghera 40 comments

Those who are still using the Dovecot's vpopmail auth driver should consider a migration to another backend, as on January 4, 2021 dovecot-2.3.13 was released and the vpopmail auth driver removed (more info here).

I'll show below how to support domain aliases with the sql driver both with all domains in the same vpopmail table and with one table for each domain (--disable-many-domains). You can find how to setup the driver in this page. A short reference to vpopmail's vconvert program is presented toward the bottom of this page, in case one is planning to switch to sql.

If you browse the comments below you'll find some other nice solutions to replace the vpopmail driver:

Saving vpopmail's aliasdomains to MySQL

As some commentators have pointed out, switching to the dovecot's sql auth driver can be painful if one has domain aliases. I will show below how to make dovecot aware of the vpopmail's aliasdomains, so that a user who tries to login with a domain alias can pass the authentication.

The idea is to save the pairs alias/domain in a new "aliasdomains" MySQL table, for example:

MariaDB [vpopmail]> SELECT * FROM aliasdomains; 
+----------------------+----------------------+ 
| alias                | domain               | 
+----------------------+----------------------+ 
| alias.net            | realdomain.net       | 
+----------------------+----------------------+

...and then modify the dovecot's sql query in order to select the user's domain from this table in case the domain is an alias or from the vpopmail table otherwise.

I patched vpopmail so that it  will transparently do the sql stuff when creating/deleting the alias in the usual way by means of the vaddaliasdomain/vdeldomain vpopmail's programs.