Re: [gentoo-user] tips on running a mail server in a cheap vps provider run but not-so-trusty admins?

[Grant Taylor]

On 8/17/20 5:33 AM, Ashley Dixon wrote:
> How many concurrent users will be connected to the mail server? How
> much traffic will the S.M.T.P.  server receive (read: how many
> e-mails  arrive  on  a  daily basis)?

My main VPS has a single digit number of clients and processes anywhere 
between 50,000 and 200,000 emails per day.  It does so without any problem.

> If you really don't trust your V.P.S. provider, and your mail server
> is small-ish, you could just skip all the trust issues and buy a
> cheap Raspberry Pi for £20 or so.

The VPS includes a globally routed IP, something that a Raspberry Pi 
doesn't inherently include.  The connectivity, including reverse DNS, is 
a big issue for running an email server.

> Running a mail server over a domestic connection presents some
> issues,  such  as dynamic I.P. ranges appearing in the Spamhaus
> blocklist, or some tyrannicalesque I.S.P.s blocking outbound port 25
> (S.M.T.P. submission port),

Nitpick:  SMTP's /submission/ port is TCP 587.  "Submission" is a very 
specific term in SMTP nomenclature.  Specifically client's /submitting/ 
email into the SMTP ecosystem.  Server to server happens over the SMTP port.

I believe you mean the regular SMTP port, TCP 25.

> but it is possible to have a smooth, self-administered mail server,
> providing you can  put  in  the time and effort.

Agreed.

ProTip:  Running an email server is about more than just SMTP.  You 
really should have a good working understanding of the basics of 
multiple protocols and technologies that are part of the email ecosystem:

  - SMTP protocol
  - DNS protocol
  - POP3 and / or IMAP client access protocols
  - MTA
  - LDA
  - Virus filtering
  - Spam filtering
  - SPF
  - DKIM
  - DMARC
  - RBLs
  - RWLs
  - Client operations
  - email ecosystem nomenclature

That's just the short list.

When I say "have a good working understanding", I mean that you should 
be able to provide a 101 level 30-90 second description of each of those 
items.  Actual understanding, not just wrote memorization.

> I have been doing it myself for a few years with Courier and Postfix

I've been doing it for 20+ years with multiple MTAs, multiple client 
MUAs, multiple 3rd part <bla> as a service providers.  None of any of 
the components is difficult itself.  The annoying thing comes when you 
try to get multiple to interact well with each other.

> (although I wouldn't recommend Courier; Dovecot is far superior).

To each their own.  I chose Courier because it could do things that 
Dovecot couldn't (at the time I made the decision) and fit my needs 
considerably better.

Some of the things that you need to make decisions about are learned 
about with experience, usually unfavorable experience.  As in "crap, I 
don't like the way that works".  Thus you make a new decision.

There is (or used to be) much debate about should email accounts be real 
and have backing Unix (OS) level accounts, or should they be virtual and 
fall under the auspice of one single Unix (OS) level account that the 
client access protocol daemon(s) run as.  From a purely email 
perspective, this might not matter.  But it really starts to matter if 
you want friends that have email with you to also be able to host a web 
site with you and need to connect in to manage their site, thus needing 
a Unix (OS) level account to do so.

> What do you think?

There are MANY different ways that you can combine the things I listed 
above.  It is usually a personal choice.  Some things that work out well 
in one configuration are completely non-applicable or even detrimental 
in another configuration.

There are many recopies to get started.

You really need to start somewhere, learn as you go, and make your own 
choices.



-- 
Grant. . . .
unix || die