Fallback from the Submission port to the SMTP port
Should I Use a Default SMTP Port for Email Sending? | Mailtrap Blog
How to Choose the Right SMTP Port (Port 25, 587, 465, or 2525)
MailEnable Submission Port 587 and SMTPS 465 Port With SSL/TLS
TCP/IP - SMTP ( サブミッションポートとSMTP認証 )
Which SMTP Port Should I Use? Understanding Ports 25, 465, & 587 | Mailgun
FROM JULY 3rd, 2019 - NEW RULES FOR ALL CARGO IN TANZANIA PORTS - Africa Logistic Network - FROM JULY 3rd, 2019 – NEW RULES FOR ALL CARGO IN TANZANIA PORTS - Africa Logistic Network