Какой почтовый сервер выбрать?

#!/bin/bash


USER=xxxxxxxxxxx
PASSWORD="xxxxxxxxxxxxxxxxxxxxxx"
DATABASE=xxxxxxxxxxx
CONNECTION="postgresql://$USER:$PASSWORD@localhost:5432/$DATABASE?sslmode=require"

DOMAIN="example.com"

function usage() {

    cat  << EOF
This script is used for alias managment for postfix with PostgreSQL installation                                                        .

Usage: aliases <command>
Commands:
list
        output all aliases

all
        output all aliases and emails without aliases

add <valid email> <alias>
        add new alias <alias> for email <valid email>

remove <valid email> <alias> [--force]
        remove alias <alias> for email <valid email>

find <something>
        shows all email and aliases contains text <something>
check
        shows all broken aliases.
EOF
}

function error() {
    echo "Error: $1"
    exit
}

function check_email_exists() {

    if [ -n "$1" ]; then
        local RES=$(psql -q -n -t ${CONNECTION} -c "select count(*) from forwardings where address='$1' and forwarding=address and is_alias=0") #" MC Parser FIX
        echo $RES | tr -d "\r\n\t "
    else
        echo 0
    fi;
}

function check_alias_exists() {

    if [ -z "$1"  -o  -z "$2" ]; then
        echo 0
    else
        local RES=$(psql -q -n -t ${CONNECTION} -c "select count(*) from forwardings where address='$2' and forwarding='$1' and is_alias=1") #" MC Parser FIX
        echo $RES | tr -d "\r\n\t "
    fi;
}

function run_sql() {
    psql -1 -q -n $2 ${CONNECTION} -c "$1"
}

CMD=$1
EMAIL=$2
ALIAS=$3
FORCE=$4

    case "x$CMD" in
    "xall")
            run_sql "select address \"virtual email\",forwarding \"original email\",is_alias from forwardings"
            exit
        ;;

    "xlist")
            run_sql "select address \"virtual email\",forwarding \"original email\" from forwardings where is_alias = 1"
            exit
        ;;
    "xcheck")
            run_sql "select a.address \"virtual email\",a.forwarding \"original email\",a.is_alias from forwardings a left join forwardings b on a.forwarding=b.address where b.forwarding is null"
            exit
        ;;
    "xfind")
            EMAIL=$(echo ${EMAIL} | tr -d '\"\r\n\t\a\%\$\!\\\/\^\&\*{}[]#()~') # ' MC PARSER FIX
            echo "Searchong for '${EMAIL}'"
            run_sql "select address \"virtual email\",forwarding \"original email\", is_alias from forwardings where address like '%${EMAIL}%' or forwarding like '%${EMAIL}%'" "-t"
            exit
        ;;

    "xadd")
            if [ "$EMAIL" == "$ALIAS" ]; then
                error "email and alias can't be equal!"
            fi;

            if [ "$(check_email_exists "$EMAIL")" == "0" ]; then
                error "email '$EMAIL' doesn't exists! Try lowercase."
            fi;

            if [ "$(check_alias_exists "$EMAIL" "$ALIAS")" !=  "0" ]; then
                error "alias '$ALIAS' for email '$EMAIL' already exists!"
            fi;

            run_sql "INSERT INTO forwardings (address, forwarding, domain, is_alias,active) VALUES ('$ALIAS', '$EMAIL', '$DOMAIN', 1,1);" "-t"
            exit
        ;;

    "xremove")
            if [ "$(check_email_exists "$EMAIL")" == "0" ]; then
                if [ "$FORCE" != "--force" ]; then
                    error "email '$EMAIL' doesn't exists! Try lowercase."
                fi;
            fi;

            if [ "$(check_alias_exists "$EMAIL" "$ALIAS")" ==  "0" ]; then
                error "alias '$ALIAS' for email '$EMAIL' doesn't exists!"
            fi;

            if [ "$EMAIL" == "$ALIAS" ]; then
                error "email and alias can't be equal!"
            fi;

            run_sql "delete from forwardings where address ='$ALIAS' and forwarding='$EMAIL' and is_alias=1;" "-t"
            exit
        ;;

    *)
        usage
        exit
        ;;
    esac;