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GitHub - lettier/smtpclient: A simple SMTP client that uses either port 25 or 587 with TLS authentication.
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exchange - edge server 2016 not receiving email, blocked ports? - Server Fault
SMTP Ports - Secure SSL Email Ports (25,465,587 & 2525)
Why does Gmail (add accounts) using SMTP server recommend SSL instead of TLS? - Information Security Stack Exchange
Which SMTP Port to Use for Email: 25, 587, 465, or 2525?
Which SMTP Port to Use for Email: 25, 587, 465, or 2525?
Secure SMTP Optimization
Which SMTP Port Should I Use? Understanding Ports 25, 465, & 587 | Mailgun
Which SMTP Port to Use for Email: 25, 587, 465, or 2525?
Enable Opportunistic TLS in IIS SMTP Service - Tutorial
What's an SMTP port & how to choose the right one | Postmark
Which SMTP Port to Use for Email: 25, 587, 465, or 2525?
Admin settings - SMTP | Looker | Google Cloud
Send mail through your SMTP server - Gmail Community
