Collecting and sorting email attachments using Fetchmail + Procmail + uudeview

Background

At work, I received a task from a colleague about the need to resolve the issue of saving attachments to letters (arriving at a specific email address) and saving them on a file server. The subject of the letter contains an abbreviation that must be specified in the name of the directory where attachments will be saved.

I found several articles on the Internet using these tools, but for the most part they did not allow me to do what was intended and I had to add a configuration file that allowed us to save files on a network share.

What and why

Fetchmail – we need it to collect letters from the mail server; setting up this utility as a whole does not have any complicated points. More details here.

Procmail is an email delivery agent that allows you to process a letter. More details at the link.

We also need a utility uudeview – This utility works with binary files and is needed to process attachments.

Installation and configuration of utilities

I chose server ubuntu 22.04, we install:

sudo apt update

sudo apt upgrade

apt install fetchmail procmail uudeview cifs-utils

and create a directory where everything will live

mkdir mail

Create a fetchmail.log file in the created mail directory

touch mail/fetchmail.log

grant access to it:

chmod 700 mail/fetchmail.log
chown user:user mail/fetchmail.log

connect a network folder (in my case the file server runs on Windows Server, so the connection is via the samba protocol via cifs)
Open the file /etc/fstab

mcedit /etc/fstab

And add a line (first the path to the file server, and then the mount point)

//*путь к серверу* /mnt cifs defaults,uid=1000,gid=1000,rw,credentials=/home/user/.smbclient 0 0

Create a file with credentials

mount -a

open the file

mcedit .smbclient

and add lines with data (indicate your account information):

username=user
password=password
domain=example.com

We mount

mount -a

Next, configure fetchmail:

mcedit ~/.fetchmailrc

In case of IMAP connection

poll mail.example.com
  port 993
  proto IMAP
  user "user"
  password "password"
  ssl
  mda "/usr/bin/procmail -d %T"
  set syslog set logfile "mail/fetchmail.log"

where mail.example.com is the mail server to which you will receive mail
The rest, I think, is clear and understandable)

in case of POP3 connection

poll mail.example.com
  port 995
  proto POP3
  user "user"
  password "password"
  ssl
  mda "/usr/bin/procmail -d %T"
  set syslog set logfile "mail/fetchmail.log"

We register access to the file:

chmod 700 .fetchmailrc
chown user:user .fetchmailrc

Now let's move on to setup Procmail

mcedit ~/.procmailrc

and add the following:

SHELL=/usr/bin/sh

subject =`cat | egrep "^Subject:" | awk '{ print $2 }'`
:0
* ^Subject:[ ].+[a-z0-9]
* ^Content-Type:

| mkdir /mnt/${subject} ;\
 uudeview -i +a +o -p /mnt/$subject -

We register access to the file:

chmod 700 .procmailrc
chown user:user .procmailrc

I explain:

this config file checks letters on the mail server and creates a folder with the name of the subject and saves attachments from the letter into it

Launch

Now, after all the settings, we send a test email with an attachment and run the command:

  fetchmail -kv

If necessary, add command execution to the task scheduler

open the scheduler:

crontab -e

and add an entry that will execute the command every minute:

*/1 * * * * /usr/bin/fetchmail -kv

We check for the presence of a new directory on the network share and attachments in them.

The final

In my case, there was a problem with the encoding; topics written in Cyrillic are saved in a crooked form, so we use the Latin alphabet; so far, a solution to this problem has not been found.

If you are not saving files on a network share, but everything is fine on the local disk, check access to the network folder.