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Hello helpful server folks,

I'm messing with iRedMail. I've mostly been successful, I think I have an SMTP problem.

I have changed RoundCube (webmail) to use BrightHouse's, my ISP's, SMTP server for outgoing. It works fine, I click send and poof, I have gmail. I can reply from gmail to my email server, and it works. It took 10 hours for the email to show up, which is a different problem, I think, but it does work.

But when I send from my server TO my own server, my ISP's Postmaster account sends me a cryptic blurb. I just got off the phone with them, and they say it "should work", and that they can't reach my pop3 server. (pop3, pop3s, imap, and imaps are all open on my router and forwarded to the server, I'm not sure what I need, I'm just covering my bases...)

pop3 and/or imap as external interfaces are just formalities, I really just want webmail to work.

Roundcube only takes one SMTP server in its configs. How can I configure Postfix to relay / forward emails to my ISP's SMTP, while taking messages bound for my own domain and processing them? Since my ISP won't let me "bounce" my emails off of it.

Maybe I'm vastly misunderstanding how e-mail works in general: To receive mail, I should only need port 25, SMTP, open to the internet, correct? Should I be concerned about some authentication failure from the outside to my relay? (My relay requires user/pass to use, my ISP's requires none.)

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closed as off topic by mdpc, Michael Hampton, Brent Pabst, rnxrx, EEAA Nov 6 '12 at 4:27

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To be blunt, this is what consultants and hosted e-mail providers are for. E-mail servers may seem easy to setup but in this day and age ensuring the proper operation and compliance of them all is difficult. –  Brent Pabst Nov 5 '12 at 14:43
    
thanks, I suppose, for saying that a difficult problem is difficult... but those consultants are mortals as well, and I'd like to gain some knowledge. –  John Nov 5 '12 at 16:10
1  
My main point is that the question(s) you were asking are not easily solvable in the Q&A mode. This would really require some one on one or deeper research into how e-mail works and the requirements surrounding it to become proficient. It's not something we can easily answer for you here. If you have specific questions regarding a tech or problem those we can certainly help you out with. –  Brent Pabst Nov 5 '12 at 16:50

1 Answer 1

up vote 0 down vote accepted

My solution isn't ideal, but it does work.

By changing Roundcube's SMTP server to my ISP's, my outbound mail doesn't get spam junked, but I can no longer email my own domain. This is because my ISP's SMTP server is not an authorized source for email from my domain.

in /etc/postfix/main.cf, the line proxy_read_maps = ... has an item $smtpd_sender_login_maps.

I removed this item and restarted postfix. Tada! I can email my own domain. What have I done, though? It seems I've opened a "security" hole in that any SMTP server sending to my domain can impersonate my users, to my users.

There is another possibility: in /etc/postfix/main.cf, there is a line defining smtpd_sender_login_maps = proxy:ldap:/etc/postfix/ldap/sender_login_maps.cf. I'm not sure exactly what I'm looking at in this file, but there is probably some way to leave the security measures in place while still allowing mail from this domain, from different SMTP servers.

Or maybe this solution is backwards, and I should always use my own SMTP, configuring it to forward when the destination is not myself.

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