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-----Original Message-----
From: ProFox [mailto:[email protected]] On Behalf Of Ken Dibble
Sent: 16 June 2016 19:34
To: [email protected]
Subject: [NF] Linux SMTP/POP Servers?

We've been running an internal email system that is built into the ClearOS 
operating system (a version of CentOS that functions as a SAMBA 3 domain 
controller) for many years. Along with the ClearOS SMTP/POP server, we've been 
running MailMan on the same machine to provide an internal listserv capability. 
Unfortunately, I'm going to have to discard ClearOS and go with a Windows AD 
domain server. I want to preserve the internal email and listserve 
functionality, and I want to run it on one of my new Linux Synology NAS clones.

There are a bazillion options for replacements and I don't have any reliable 
basis on which to evaluate them.

Do any of you have recommendations for Linux SMTP/POP server software that 
would be suitable for running an internal email system?

By "suitable for running an internal email system" I mean:

1. The system will not/cannot/must not communicate with, or be seen from, the 
internet.

The ClearOS SMTP/POP server is configured to only accept, and send, email 
within its own domain (though this may be achieved by tweaking Linux ports 
rather than directly within the email server, given the information provided in 
the next paragraph, I don't know). The host machine is behind a NATing router 
that does not have any open ports for email. I need an email server that can be 
configured in the same way.

Related to this, I would prefer the ability to configure how the SMTP server 
responds to invalid input, including messages addressed to the internet or to 
invalid internal addresses. The ClearOS server tries to send these several 
times, at increasingly long intervals, so that it takes 3 or more days to put 
out a bounce-back message, and this configuration can't be changed. I would 
rather that bounce-backs take place immediately.

2. Must provide all standard POP3 functionality (thank you, but I am not 
looking for an explanation of why I should use IMAP instead), including the 
ability to communicate with a fat Windows email client that will sometimes tell 
it to retain email on the server for a period of time.

3. Free as in beer, preferably, but if not an option, then I would be willing 
to pay a reasonable one-time license fee, not based on the number of email 
accounts, for perpetual use. I am not willing to pay for a "software as 
service" arrangement.

4. Because it is an internal server with no connection to the internet, it does 
not have to have all of the high-paranoia-level security features that an 
internet email server needs. I will cope with it if it does not pemit plain 
text authentication, but plain text authentication is perfectly adequate and 
completely safe for my purposes.

5. It doesn't have to have any built-in spam filtering.

The current CentOS SMTP/POP server has annoying spam filtering features that 
are buggy and can't be turned off. For example, zip file attachments (and 
sometimes docx and xlsx attachments, which are just zip files) go missing, and 
it can choke on other unusual file attachments. None of this nonsense is 
necessary and I would prefer for nothing to be built-in that filters spam or 
messes with attachments. If any such thing is built-in, it needs to be able to 
be turned off, and stay off.

6. If it doesn't integrate true listserv capabilities (no fudging with 
"aliases" or numerically-limited forwarding lists) like those of MailMan, then 
it needs to be compatible with MailMan.

7. Traffic requirements: I don't know much about what sort of resources a Linux 
SMTP/POP server requires. Currently we have about
120 email accounts, each with a 1 GB mailbox on the server, and the NAS will 
accommodate that without even blinking. Conceivably someday we could be looking 
at more like 250 accounts. To the extent to which that affects 
speed/responsiveness, then that's a consideration.

8. Easy to set up and configure, and if not, then EXTREMELY well- and 
reliably-documented.

9. <rant>Probably not an option, but, since I want an integrated SMTP/POP 
server, then, for the sake of the Mother of All that is Good, would it be too 
much to ask for an integrated validation system in which, just for laughs, the 
SMTP server simply compares the sender's address to the POP server's list of 
valid accounts for that domain to determine whether or not to accept and relay 
an incoming message, instead of performing bollocks-oriented "test sends" back 
to the user that will fail if the user's inbox, the state of which bears no 
rational relationship to the person's authorization, ability, or need, to use 
the SMTP server to SEND email, is full, and calling it "validation", which it 
is, emphatically, NOT?</rant>

Thanks for all of your suggestions and the benefit of your experience.

Ken Dibble
www.stic-cil.org




[excessive quoting removed by server]

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