[MlMt] Selecting default SMTP server

Bill Cole mmlist-20120120 at billmail.scconsult.com
Sat Jul 24 23:59:14 EDT 2021

On 2021-07-24 at 23:03:04 UTC-0400 (Sun, 25 Jul 2021 03:03:04 +0000)
Antonio Leding <mailmate at lists.freron.com>
is rumored to have said:

> “…not feasible to send mail claiming to be from a particular 
> address through any arbitrarily chosen mail server…”
> Mostly true but there’s ways around such hindrances…
> https://www.wpoven.com/blog/free-smtp-servers-sending-emails/

All of those require you to set up accounts with the providers in 
question. For example, you cannot simply decide to route your mail 
through Google's mail servers without having a Google account and 
configuring it to allow you to send mail using that account with sender 
addresses that are not hosted at Google.

So: not quite "arbitrarily chosen."

> I haven’t used any of my “assigned” SMTP servers since 2000.  
> And since 2013, been using a combo of Amazon’s SES or my own 
> Postfix…the latter is especially nice if one wants to use a 
> non-standard port...

Sure, but you are almost surely using mail submission (port 587 or 465, 
with mandatory TLS encryption and authentication and DKIM signatures 
added with "d=amazonses.com") and you have published a SPF record in DNS 
for leding.net which explicitly declares that your mail may legitimately 
be coming out of SES.

Back before spam was a problem, it was possible to submit mail without 
authentication through nearly all SMTP servers, using whatever envelope 
sender and/or From address you felt like using with any server. This has 
evolved over time to the current situation where authentication (and 
hence server-specific account setup) is almost universally required 
along with TLS encryption. Some mail clients (including, at least in the 
past, Apple Mail) have configured submission (i.e. SMTP-like) servers 
independently of IMAP accounts and allowed users to arbitrarily select 
which outbound path to use with each message, regardless of which sender 
address is used. That is not generally safe today, but it was once 
entirely reasonable.

> - - -
> On 24 Jul 2021, at 19:47, Bill Cole wrote:
>> On 2021-07-24 at 21:15:55 UTC-0400 (Sat, 24 Jul 2021 18:15:55 -0700)
>> Ralph Alvy <mailmate at lists.freron.com>
>> is rumored to have said:
>>> If I have more than one Source Acct, how do I tell Mailmate with 
>>> SMTP server to use for outgoing mail?
>> Each account has its own exclusive SMTP Server settings. This is good 
>> because on the modern Internet, it is not feasible to send mail 
>> claiming to be from a particular address through any arbitrarily 
>> chosen mail server. It might work, but more likely your mail would be 
>> rejected or worse: dropped silently.

Bill Cole
bill at scconsult.com or billcole at apache.org
(AKA @grumpybozo and many *@billmail.scconsult.com addresses)
Not Currently Available For Hire

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