LinuxQuestions.org - Neomutt - "sasl authentication failed"

Yesterday I installed the Mail-in-a-box server in a Debian9 vps. It comes with roundcube and the setup with webmail has been running well since the beginning.
I then wanted to access the server through neomutt on my home computer.
For that, I wrote the following muttrc:

Quote:

set from = "mic@homebythefire.me"
set realname = "Miguel Caldas"
set imap_user = "mic@homebythefire.me"
set imap_pass = "xxxx"
set edit_headers = yes

set smtp_url ="smtp://mic@homebythefire.me@box.homebythefire.me:587/"
set smtp_pass = "xxxx"
set ssl_starttls = yes

set spoolfile="imaps://mic@homebythefire.me:xxxx@box.homebythefire.me/"
set folder="imaps://box.homebythefire.me/"
set tmpdir = "/tmp"
set record = "Sent"
set mbox = "+mbox"
set postponed = "Drafts"

set ssl_starttls=yes
set ssl_force_tls=yes

unset imap_passive
set imap_check_subscribed
set mail_check=60
set timeout=10
set header_cache=~/.hcache

set wait_key = no
set mbox_type = Maildir
set timeout = 3
set delete
unset confirmappend
set quit

set editor='tilde'

color normal white blue
color progress blue white
color hdrdefault green white

When I opened neomutt I was indeed seeing the server's inbox. But when I tried to send a mail, after the message

Quote:

Authenticating PLAIN

get this error message:

Quote:

SASL authentication failed

.

This is the server's Postfix "main.cf" file:

Quote:

# See /usr/share/postfix/main.cf.dist for a commented, more complete version

# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

#smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
smtpd_banner=$myhostname ESMTP Hi, I'm a Mail-in-a-Box (Ubuntu/Postfix; see https://mailinabox.email/)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h
delay_warning_time=3h

readme_directory = no

# See http://www.postfix.org/COMPATIBILITY_README.html -- default to 2 on
# fresh installs.
compatibility_level = 2

# TLS parameters
#smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_cert_file=/home/user-data/ssl/ssl_certificate.pem
#smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_key_file=/home/user-data/ssl/ssl_private_key.pem
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.

#smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
smtpd_relay_restrictions=
permit_sasl_authenticated,
permit_mynetworks
check_relay_domains
myhostname = box.homebythefire.me
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
#mydestination = $myhostname, localdomain, localhost, localhost.localdomain, localhost
mydestination=localhost
relayhost =
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128, 192.168.4.1 to 192.168.4.253
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
smtp_bind_address=95.179.131.156
smtp_bind_address6=2001:19f0:5001:1e69:5400:1ff:fede:1654
maximal_queue_lifetime=2d
bounce_queue_lifetime=1d
smtpd_tls_security_level=may
smtpd_tls_auth_only = no
smtpd_tls_dh1024_param_file=/home/user-data/ssl/dh2048.pem
smtpd_tls_protocols=!SSLv2,!SSLv3
smtpd_tls_ciphers=medium
smtpd_tls_exclude_ciphers=aNULL,RC4
smtpd_tls_received_header=yes
smtp_tls_protocols=!SSLv2,!SSLv3
smtp_tls_mandatory_protocols=!SSLv2,!SSLv3
smtp_tls_ciphers=medium
smtp_tls_exclude_ciphers=aNULL,RC4
smtp_tls_security_level=dane
smtp_dns_support_level=dnssec
smtp_tls_CAfile=/etc/ssl/certs/ca-certificates.crt
smtp_tls_loglevel=2
virtual_transport=lmtp:[127.0.0.1]:10025
smtpd_sender_restrictions=reject_non_fqdn_sender,reject_unknown_sender_domain,reject_authenticated_s ender_login_mismatch,reject_rhsbl_sender dbl.spamhaus.org
smtpd_recipient_restrictions=permit_sasl_authenticated,permit_mynetworks,reject_rbl_client zen.spamhaus.org,reject_unlisted_recipient,check_policy_service inet:127.0.0.1:10023
message_size_limit=134217728
smtpd_sasl_type=dovecot
smtpd_sasl_path=private/auth
smtpd_sasl_auth_enable=yes
smtpd_sender_login_maps=sqlite:/etc/postfix/sender-login-maps.cf
virtual_mailbox_domains=sqlite:/etc/postfix/virtual-mailbox-domains.cf
virtual_mailbox_maps=sqlite:/etc/postfix/virtual-mailbox-maps.cf
virtual_alias_maps=sqlite:/etc/postfix/virtual-alias-maps.cf
local_recipient_maps=$virtual_mailbox_maps
smtpd_milters=inet:127.0.0.1:8891 inet:127.0.0.1:8893
non_smtpd_milters=$smtpd_milters
milter_default_action=accept

I am very new to everything about mail servers, so I really have no idea how to troubleshoot this.

Any help would be greatly appreciated