Question Mail messages sequence via MSAs ?

johnyb98

Distinguished
Apr 3, 2015
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Hello dear members.
When a user creates a mail message, when pressing"send", mail passes OBLIGATORILY via ISP's submission agent (MSA)? So, if I have a domain, and eg with Linode+domain I create a SMTP relay agent (MDA), although if I have asked Linode (and Linode has agreed) and opened my IN+OUT 25 SMTP server's ports), the first step is that mail will pass through ISP's MSA?

Thank you!
 

kanewolf

Titan
Moderator
Hello dear members.
When a user creates a mail message, when pressing"send", mail passes OBLIGATORILY via ISP's submission agent (MSA)? So, if I have a domain, and eg with Linode+domain I create a SMTP relay agent (MDA), although if I have asked Linode (and Linode has agreed) and opened my IN+OUT 25 SMTP server's ports), the first step is that mail will pass through ISP's MSA?

Thank you!
What SMTP server address do you have configured in your mail client? Traffic should be routed there as IP traffic. The ISP should just see it as IP (and preferably SSL encrypted ) traffic.
 

johnyb98

Distinguished
Apr 3, 2015
114
1
18,585
No client setup. I am trying to understand the whole mail server build (domain registration, MUA, MSA, MDA, MX records, SPF, DKIM, DMARC, ports, submission, relay, ISP Port 25 when open vs when closed, why and when Port 25 is in and when out) and all this. I want to build my own mail server via a domain registration. But if I miss even a tiny detail, the whole thing will not work.