Hi @andersonvm ,
Thank you for your kind reply. It is a commercial xcloud server (I think like a Vmware virtual machine). I installed Centos 7 from scratch. Then Virtualmin, Apache, Php, MariaDb, Postfix, Dovecot imap server etc.
The SSL certificate is requested from Let’s Encrypt authority and used on all services.
I use it solely for OJS journals, and but can run anything.
I follow Postmaster emails and the emails generally reach the recipients. They send dmarc-support reports regularly. For ex;
<count>33</count>
<policy_evaluated>
<disposition>none</disposition>
<dkim>**pass**</dkim>
<spf>**pass**</spf>
</policy_evaluated>
</row>
<identifiers>
<header_from>akademisyen.net</header_from>
</identifiers>
<auth_results>
<dkim>
<domain>akademisyen.net</domain>
<result>**pass**</result>
<selector>academician</selector>
</dkim>
<spf>
<domain>akademisyen.net</domain>
<result>**pass**</result>
</spf>
With your port settings, I get these errors in error log 
[11-Feb-2021 22:13:27 Europe/Istanbul] Connection: opening to ssl://smtp.gmail.com:587, timeout=300, options=array()
[11-Feb-2021 22:13:27 Europe/Istanbul] Connection failed. Error #2: stream_socket_client(): SSL operation failed with code 1. OpenSSL Error messages:
error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol [/home/adlitip/public_html/lib/pkp/lib/vendor/phpmailer/phpmailer/src/SMTP.php line 375]
[11-Feb-2021 22:13:27 Europe/Istanbul] Connection failed. Error #2: stream_socket_client(): Failed to enable crypto [/home/adlitip/public_html/lib/pkp/lib/vendor/phpmailer/phpmailer/src/SMTP.php line 375]
[11-Feb-2021 22:13:27 Europe/Istanbul] Connection failed. Error #2: stream_socket_client(): unable to connect to ssl://smtp.gmail.com:587 (Unknown error) [/home/adlitip/public_html/lib/pkp/lib/vendor/phpmailer/phpmailer/src/SMTP.php line 375]
[11-Feb-2021 22:13:27 Europe/Istanbul] SMTP ERROR: Failed to connect to server: (0)
[11-Feb-2021 22:13:27 Europe/Istanbul] SMTP connect() failed. Troubleshooting · PHPMailer/PHPMailer Wiki · GitHub
When I set protocol to tls, or change the port number, the following error lines are logged.
[11-Feb-2021 22:19:48 Europe/Istanbul] Connection: opening to smtp.gmail.com:587, timeout=300, options=array()
[11-Feb-2021 22:19:48 Europe/Istanbul] Connection: opened
[11-Feb-2021 22:19:48 Europe/Istanbul] SERVER → CLIENT: 220 smtp.gmail.com ESMTP m5sm8890843wmc.25 - gsmtp[11-Feb-2021 22:19:48 Europe/Istanbul] CLIENT → SERVER: EHLO www.adlitip.net
[11-Feb-2021 22:19:48 Europe/Istanbul] SERVER → CLIENT: 250-smtp.gmail.com at your service, [37.148.209.149]
250-SIZE 35882577
250-8BITMIME
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-CHUNKING
250 SMTPUTF8[11-Feb-2021 22:19:48 Europe/Istanbul] CLIENT → SERVER: STARTTLS
[11-Feb-2021 22:19:48 Europe/Istanbul] SERVER → CLIENT: 220 2.0.0 Ready to start TLS
[11-Feb-2021 22:19:48 Europe/Istanbul] CLIENT → SERVER: EHLO www.adlitip.net
[11-Feb-2021 22:19:48 Europe/Istanbul] SERVER → CLIENT: 250-smtp.gmail.com at your service, [37.148.209.149]
250-SIZE 35882577
250-8BITMIME
250-AUTH LOGIN PLAIN XOAUTH2 PLAIN-CLIENTTOKEN OAUTHBEARER XOAUTH
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-CHUNKING
250 SMTPUTF8[11-Feb-2021 22:19:48 Europe/Istanbul] CLIENT → SERVER: AUTH LOGIN
[11-Feb-2021 22:19:48 Europe/Istanbul] SERVER → CLIENT: 334 VXNlcm5hbWU6
[11-Feb-2021 22:19:48 Europe/Istanbul] CLIENT → SERVER: [credentials hidden]
[11-Feb-2021 22:19:48 Europe/Istanbul] SERVER → CLIENT: 334 UGFzc3dvcmQ6[11-Feb-2021 22:19:48 Europe/Istanbul] CLIENT → SERVER: [credentials hidden]
[11-Feb-2021 22:19:49 Europe/Istanbul] SERVER → CLIENT: 534-5.7.14 <https://accounts.google.com/signin/continue?sarp=1&scc=1&plt=AKgnsbs
534-5.7.14 b0O-iHug57Uyf9cRZj4pESBXp_AwoCnxozM8KH-K7wdxiVMVplFK6OeLh2K5BkSngw7CG
534-5.7.14 fxexhw2bFtjqKNkGpIj9ttQxtgpP7xOZx0f31GUwpiI3zu-cJ-vsB403gw13eCbF>
534-5.7.14 Please log in via your web browser and then try again.
534-5.7.14 Learn more at
534 5.7.14 Can't sign in to your Google Account - Gmail Help m5sm8890843wmc.25 - gsmtp[11-Feb-2021 22:19:49 Europe/Istanbul] SMTP ERROR: Password command failed: 534-5.7.14 <https://accounts.google.com/signin/continue?sarp=1&scc=1&plt=AKgnsbs
534-5.7.14 b0O-iHug57Uyf9cRZj4pESBXp_AwoCnxozM8KH-K7wdxiVMVplFK6OeLh2K5BkSngw7CG
534-5.7.14 fxexhw2bFtjqKNkGpIj9ttQxtgpP7xOZx0f31GUwpiI3zu-cJ-vsB403gw13eCbF>
534-5.7.14 Please log in via your web browser and then try again.
534-5.7.14 Learn more at
534 5.7.14 Can't sign in to your Google Account - Gmail Help m5sm8890843wmc.25 - gsmtp[11-Feb-2021 22:19:49 Europe/Istanbul] SMTP Error: Could not authenticate.
[11-Feb-2021 22:19:49 Europe/Istanbul] CLIENT → SERVER: QUIT[11-Feb-2021 22:19:49 Europe/Istanbul] SERVER → CLIENT: 221 2.0.0 closing connection m5sm8890843wmc.25 - gsmtp
[11-Feb-2021 22:19:49 Europe/Istanbul] Connection: closed
[11-Feb-2021 22:19:49 Europe/Istanbul] SMTP connect() failed. Troubleshooting · PHPMailer/PHPMailer Wiki · GitHub
[11-Feb-2021 22:19:49 Europe/Istanbul] SMTP connect() failed. Troubleshooting · PHPMailer/PHPMailer Wiki · GitHub
Although I’m not sure, I think the following lines support my opinion: “SMTP Error: Could not authenticate.”
Long story short, big brothers are happy when we use their services, and pay them.
Regards,