>>>> I don't see why local Squirrelmail won't send mail over 587, >>>> but remote Thunderbird will. Squirrelmail also won't send mail over >>>> port 25, but it will send mail over 465. >>> >>> >>> Do you have a new-enough SquirrelMail? From the looks of it, the only >>> version >= 1.5.1 is the development snapshot. (Do you know about Roundcube?) >> >> OK, that must be why Squirrelmail can't send mail over 587. I'm on >> the latest version in Portage. You spelled it out for me before but I >> didn't pick up on it. Since 587 uses STARTTLS, I would have thought I >> could connect unencrypted but apparently encryption is required there? >> >> Is Squirrelmail failing to send mail over port 25 because >> authentication isn't allowed on port 25? If so, do I need a dedicated >> port for unencrypted local Squirrelmail mail? > > I don't think you're really getting the significance of port 587 vs. port 25.
I think you're right. > 587 can be used encrypted or unencrypted, authenticated (preferably) or > not... you could for instance just limit 587 connections from a particular > subnet, etc. Why then won't Squirrelmail send mail on port 587 unencrypted with "Secure SMTP (TLS) : false"? I get: 530 5.7.0 Must issue a STARTTLS command first > But the main difference is this: > > 587 is used by MUA's (i.e. clients) to submit *outbound* messages to your MTA > (relay). > > 25 is used by your MTA to receive *incoming* messages from other > administrative domains (organizations). Port 25 is never used to submit outbound messages? If not, I'm confused as to why Squirrelmail describes its "SMTP Port" setting this way: This is the port to connect to for SMTP. Usually 25. - Grant
