eb 01 05:58:22 archiso neomutt[15862]: DIGEST-MD5 common mech free
Hi,
I just installed Mail-in-a-box in a Debian 9 vps, and it's working perfectly.
i wanted to access it through my Neomutt client on my home computer, so I wrote the following muttrc:

set from = "'_user'_@'_my_domain_'"
set realname = "'_my_name_'"
set imap_user = "'_user'_@'_my_domain_'"
set imap_pass = "'_my_password_'"
set edit_headers = yes

set smtp_url ="'_user'_@'_my_domain_':587/"
set smtp_pass = "'_my_password_'"
set ssl_starttls = yes

set spoolfile="imaps://'_my_domain':'_my_password''@'my_hostname'/"
set folder="imaps://'my_hostname'/"
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'

When I reentered neomutt I had access to my mail-in-a-box account.
When I tried to send a mail through it, it got to

Authenticating PLAIN

and then served the

 SASL authentication failed message.

Below logs of when I tried to send the email:

Feb 01 05:58:30 archiso postfix/qmgr[3334]: 2EF283260590: from=<mic@box.homebythefire.me>, size=326, nrcpt=1 (queua>

Feb 01 05:58:30 archiso postfix/qmgr[3334]: CA46D326059E: from=<mic@box.homebythefire.me>, size=326, nrcpt=1 (queue a>
Feb 01 05:58:30 archiso postfix/qmgr[3334]: 49CAC3260589: from=<mic@box.homebythefire.me>, size=287, nrcpt=1 (queue a>
Feb 01 05:58:30 archiso postfix/qmgr[3334]: A8A12326059A: from=<mic@box.homebythefire.me>, size=326, nrcpt=1 (queue a>
Feb 01 05:58:30 archiso postfix/smtp[15932]: smtp_stream_setup: maxtime=300 enable_deadline=0
Feb 01 05:58:30 archiso postfix/smtp[15934]: smtp_stream_setup: maxtime=300 enable_deadline=0
Feb 01 05:58:30 archiso postfix/smtp[15935]: smtp_stream_setup: maxtime=300 enable_deadline=0
Feb 01 05:58:30 archiso postfix/smtp[15933]: smtp_stream_setup: maxtime=300 enable_deadline=0
Feb 01 05:58:31 archiso postfix/smtp[15932]: vstream_buf_get_ready: fd 17 got 104
Feb 01 05:58:31 archiso postfix/smtp[15932]: < box.homebythefire.me[95.179.131.156]:587: 220 box.homebythefire.me ESM>
Feb 01 05:58:31 archiso postfix/smtp[15932]: > box.homebythefire.me[95.179.131.156]:587: EHLO archiso.localdomain
Feb 01 05:58:31 archiso postfix/smtp[15932]: vstream_fflush_some: fd 17 flush 26
Feb 01 05:58:31 archiso postfix/smtp[15934]: vstream_buf_get_ready: fd 17 got 104
Feb 01 05:58:31 archiso postfix/smtp[15934]: < box.homebythefire.me[95.179.131.156]:587: 220 box.homebythefire.me ESM>
Feb 01 05:58:31 archiso postfix/smtp[15934]: > box.homebythefire.me[95.179.131.156]:587: EHLO archiso.localdomain
Feb 01 05:58:31 archiso postfix/smtp[15934]: vstream_fflush_some: fd 17 flush 26
Feb 01 05:58:31 archiso postfix/smtp[15935]: vstream_buf_get_ready: fd 17 got 104
Feb 01 05:58:31 archiso postfix/smtp[15935]: < box.homebythefire.me[95.179.131.156]:587: 220 box.homebythefire.me ESM>
Feb 01 05:58:31 archiso postfix/smtp[15935]: > box.homebythefire.me[95.179.131.156]:587: EHLO archiso.localdomain
Feb 01 05:58:31 archiso postfix/smtp[15935]: vstream_fflush_some: fd 17 flush 26
Feb 01 05:58:31 archiso postfix/smtp[15932]: vstream_buf_get_ready: fd 17 got 158
Feb 01 05:58:31 archiso postfix/smtp[15932]: < box.homebythefire.me[95.179.131.156]:587: 250-box.homebythefire.me
Feb 01 05:58:31 archiso postfix/smtp[15932]: < box.homebythefire.me[95.179.131.156]:587: 250-PIPELINING
Feb 01 05:58:31 archiso postfix/smtp[15932]: < box.homebythefire.me[95.179.131.156]:587: 250-SIZE 134217728
Feb 01 05:58:31 archiso postfix/smtp[15932]: < box.homebythefire.me[95.179.131.156]:587: 250-VRFY
Feb 01 05:58:31 archiso postfix/smtp[15932]: < box.homebythefire.me[95.179.131.156]:587: 250-ETRN
Feb 01 05:58:31 archiso postfix/smtp[15932]: < box.homebythefire.me[95.179.131.156]:587: 250-STARTTLS
Feb 01 05:58:31 archiso postfix/smtp[15932]: < box.homebythefire.me[95.179.131.156]:587: 250-ENHANCEDSTATUSCODES
Feb 01 05:58:31 archiso postfix/smtp[15932]: < box.homebythefire.me[95.179.131.156]:587: 250-8BITMIME
Feb 01 05:58:31 archiso postfix/smtp[15932]: < box.homebythefire.me[95.179.131.156]:587: 250-DSN

I'm very new to configuring a mail server, so I'm unsure on how to progress.
I imagine that dovecot (or Postfix, for all that I know), don't recognize the mail client and stop the process, but I have no idea on how to proceed and I didn't find anything on google that someone as ignorant as me could use.

Any help would be greatly appreciated.
Thanks
Feb 01 05:58:31 archiso postfix/smtp[15932]: < box.homebythefire.me[95.179.131.156]:587: 250 SMTPUTF8
Feb 01 05:58:31 archiso postfix/smtp[15932]: server features: 0x20901f size 134217728