Issue SMTP connection problem with Gmail

[Ian Welerson]

Hello,
I have the Plesk Onyx 17.0.17 Update # 12, CentOS 6.8 (Final), and I'm having problems with SMTP authentication on the Gmail web client.
The connection via POP3 is working perfectly and the emails are being received in my Gmail account, but the connection through SMTP is not being made.
When I try to make the connection in "Settings> Accounts and Import> Add another email adress" error occurs: "Could not reach server. Please double-check the server and port number."

I'm using the settings:
SMTP Server: smtp.welerson.com.br
Port: 587
Secured connection using TLS.

On the server I'm using Postfix.

The log from Postfix is:

Jan  2 10:13:31 vps111143 postfix/smtpd[24346]: warning: hostname no-reverse-dns-configured.com does not resolve to address 89.248.171.132
Jan  2 10:13:31 vps111143 postfix/smtpd[24346]: connect from unknown[89.248.171.132]
Jan  2 10:13:31 vps111143 postfix/smtpd[24346]: disconnect from unknown[89.248.171.132]
Jan  2 10:16:51 vps111143 postfix/anvil[24349]: statistics: max connection rate 1/60s for (smtp:89.248.171.132) at Jan  2 10:13:31
Jan  2 10:16:51 vps111143 postfix/anvil[24349]: statistics: max connection count 1 for (smtp:89.248.171.132) at Jan  2 10:13:31
Jan  2 10:16:51 vps111143 postfix/anvil[24349]: statistics: max cache size 1 at Jan  2 10:13:31
Jan  2 10:33:07 vps111143 postfix/smtpd[25853]: connect from unknown[218.189.140.2]
Jan  2 10:33:08 vps111143 postfix/smtpd[25853]: disconnect from unknown[218.189.140.2]
Jan  2 10:36:28 vps111143 postfix/anvil[25855]: statistics: max connection rate 1/60s for (smtp:218.189.140.2) at Jan  2 10:33:07
Jan  2 10:36:28 vps111143 postfix/anvil[25855]: statistics: max connection count 1 for (smtp:218.189.140.2) at Jan  2 10:33:07
Jan  2 10:36:28 vps111143 postfix/anvil[25855]: statistics: max cache size 1 at Jan  2 10:33:07

All Ips in log is not from me or google.

--- EDIT

After restarting server, the error appears is in SMTP Gmail Login is:

"Server returned error: "334 PDMwMDQwODg1NDIuNjk4OTM0NkB3ZWxlcnNvbi5jb20uYnI+ 535 5.7.8 Error: authentication failed: authentication failure code(535) ""

How do I get this to work?

 

[Ian Welerson]

I resolved it after testing several possible resolutions.
For anyone with the same problem, just use a resolution described in this link: https://support.plesk.com/hc/en-us/articles/213360809

Resolution[/B]
[B]Open /etc/postfix/main.cf configuration file and comment out the following lines:

#smtpd_tls_protocols = SSLv3, TLSv1
#smtpd_tls_ciphers = medium
#smtpd_tls_exclude_ciphers = aNULL
#smtpd_sasl_security_options = noplaintext
#smtpd_tls_auth_only = yes
#tls_ssl_options = NO_COMPRESSION