Im having trouble installing SMTH Auth for my ubuntu email server. I have followed ubuntu own guide for SMTH AUT (https://help.ubuntu.com/14.04/serverguide/postfix.html). But my email client thunderbird is giving this error " lost connection to SMTP-client 127.0.0.1." What could be wrong ? Thundbird was working fine prior to me adding smtp- auth. Is connection different now maybe ? tried making thunderbird use SSL for imap as well but that neither works. I restarted postfix and dovecot to find errors but both run just fine. This is my main.cf file in postfix. It looks just like the one on ubuntu guide above. Code: readme_directory = no # TLS parameters #smtpd_use_tls=yes smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache myhostname = mail.mysite.com mydomain = mysite.com alias_maps = hash:/etc/aliases alias_database = hash:/etc/aliases myorigin = $mydomain mydestination = mysite.com #relayhost = smtp.192.168.10.1.com mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 192.168.10.0/24 mailbox_size_limit = 0 recipient_delimiter = + inet_interfaces = all home_mailbox = Maildir/ mailbox_command = #SMTP AUTH smtpd_sasl_type = dovecot smtpd_recipient_restrictions=permit_mynetworks, permit_sasl_authenticated,reject_unauth_destination smtpd_sasl_local_domain = smtpd_sasl_auth_enable = yes smtpd_sasl_security_options = noanonymous broken_sasl_auth_clients = yes smtpd_tls_auth_only = no smtp_tls_security_level = may smtpd_tls_security_level = may smtp_tls_note_starttls_offer = yes smtpd_tls_key_file = /etc/ssl/private/smtpd.key smtpd_tls_cert_file = /etc/ssl/certs/smtpd.crt smtpd_tls_CAfile = /etc/ssl/certs/cacert.pem smtpd_tls_loglevel = 1 smtpd_tls_received_header = yes This my dovecot configuration at 10-master.conf Code: service imap-login { inet_listener imap { #port = 143 } inet_listener imaps { #port = 993 #ssl = yes } # Number of connections to handle before starting a new process. Typically # the only useful values are 0 (unlimited) or 1. 1 is more secure, but 0 # is faster. <doc/wiki/LoginProcess.txt> #service_count = 1 # Number of processes to always keep waiting for more connections. #process_min_avail = 0 # If you set service_count=0, you probably need to grow this. #vsz_limit = $default_vsz_limit } service pop3-login { inet_listener pop3 { #port = 110 } inet_listener pop3s { #port = 995 #ssl = yes } } service lmtp { unix_listener lmtp { #mode = 0666 } # Create inet listener only if you can't use the above UNIX socket #inet_listener lmtp { # Avoid making LMTP visible for the entire internet #address = #port = #} } service imap { # Most of the memory goes to mmap()ing files. You may need to increase this # limit if you have huge mailboxes. #vsz_limit = $default_vsz_limit # Max. number of IMAP processes (connections) #process_limit = 1024 } service pop3 { # Max. number of POP3 processes (connections) #process_limit = 1024 } service auth { unix_listener auth-userdb { #mode = 0600 #user = #group = } # Postfix smtp-auth unix_listener /var/spool/postfix/private/auth { mode = 0660 user = postfix } } service dict { # If dict proxy is used, mail processes should have access to its socket. # For example: mode=0660, group=vmail and global mail_access_groups=vmail unix_listener dict { #mode = 0600 #user = #group = } } Added "auth_mechanisms = plain login" to 10-auth.conf as well.