diff --git a/README.md b/README.md
index a6d9cc6..9e83934 100644
--- a/README.md
+++ b/README.md
@@ -103,6 +103,21 @@ Install a systemd service as user, can be useful for timers for example :
 service_install "services/myservice.service" 1
 ```
 
+### define_env
+
+Define an evirnment variable into the file `~/.config/environment`, you have to
+source this file on your `.bashrc` or your `.zprofile`.
+
+ - **input*** :
+     - `$1` : name of the variable
+     - `$2` : value, `""` if empty
+ - **output** : no value, but exit the function if the variale is already
+     defined (install) or not in file (uninstall)
+
+```
+define_env "NOTMUCH_CONFIG" "~/.config/notmuch"
+```
+
 ### Avaible variables
 
  - `$repository` : the root folder of the repository
diff --git a/examples/mail_bootstap b/examples/mail_bootstap
index cde4f3d..1aa9b82 100644
--- a/examples/mail_bootstap
+++ b/examples/mail_bootstap
@@ -37,3 +37,6 @@ install_service "services/mail.timer" 1
 
 # Symblink an executable to $HOME\.local\bin\
 install_bin "bin/check_mails.sh"
+
+# Define the environment variable for Notmuch
+define_env "NOTMUCH_CONFIG" "~/.config/notmuch"
diff --git a/src/dotinstall.sh b/src/dotinstall.sh
index 91f8c36..5126c4e 100755
--- a/src/dotinstall.sh
+++ b/src/dotinstall.sh
@@ -6,7 +6,7 @@ BIN_DIRECTORY="${HOME}/.local/bin/"
 LIB_DIRECTORY="${HOME}/.local/lib/"
 SYD_DIRECTORY="${HOME}/.config/systemd/user"
 DOTREPO="${HOME}/.config/dotrepo/"
-
+ENV_FILE="${HOME}/.config/environment"
 
 # DEFAULT VALUES
 OVERWRITE_DIRECTORY=0
@@ -281,6 +281,32 @@ install_bin ()
     fi
 }
 
+define_env ()
+{
+    # Put a couple name value into $ENV_FILE file or remove it
+    # on uninstall mode
+    # $1 variable name
+    # $2 value
+
+    [ -z $1 ] && { error "You must define a name"; return; }
+    [ ! -f $ENV_FILE ] && touch $ENV_FILE
+    if [ $install -eq 1 ]
+    then
+        printf "\nCreate an environment variable %s : " "$1"
+        [ $(grep -c -m 1 $1 $ENV_FILE) -eq 1 ] && { error "already exist"; return; }
+        local line
+        line="export ${1}=\"${2}\""
+        echo "$line" >> $ENV_FILE
+        printf "\e[32mdone\e[0m\n"
+    else
+        printf "\nRemove an environment variable %s : " "$1"
+        [ $(grep -c -m 1 $1 $ENV_FILE) -eq 0 ] && { error "not exist"; return; }
+        sed -i "/^export $1=*/d" $ENV_FILE
+        printf "\e[32mdone\e[0m\n"
+
+    fi
+}
+
 ## create bin directory
 [ ! -d $BIN_DIRECTORY ] && mkdir -p $BIN_DIRECTORY || printf "bin exist\n"