I am able to turn off authentication and send an email to one of my
other email accounts on the same server, but I am still not able to
send email to other servers. The reported error is "550 without
authentication". My hosting provider is not being much help. They
just see it as a problem of using a crappy email program.
When sending e-mails between accounts at the same e-mail provider, it is
unlikely that SMTP is employed in the message transfer. Instead
internal routing is used to link the message to other internal accounts.
When you look at the Received headers for an internally routed message,
you'll see it never left their domain and didn't pass out through an
SMTP server. It's all internal routing. Depends on how they set up
their boundary SMTP server (the one that sends outside their domain).
I wish I understood the use of Stunnel better. I'm not sure if it will help
with this problem or if I can even run it under Windows.
Been a long time but I used sTunnel on Windows XP and it worked as long
as you get both the client and sTunnel proxy configured correctly.
Client has to connect to sTunnel, not to the e-mail server, and the
client must not use encryption when connecting to the sTunnel proxy. In
the sTunnel config, you define which inbound connections go to which
outbound connections, sort of like a mapping of in to out. Its config
file has "name=value" pairs that map which input connect goes to what
output connect.
Make sure your client doesn't encrypt its traffic for its connection to
sTunnel (configured in the account you define within your client).
sTunnel does the encryption to the server. Some examples are at:
https://www.stunnel.org/examples.html
My recollection was when having multiple e-mail clients use sTunnel that
you had them connect to different listening ports for sTunnel. Or maybe
that was just me to keep them separate. From what I see at the
examples, you really only need to define to where sTunnel will connect
(the e-mail servers). No login credentials are including in the config
because those get stripped (parsed out) from the non-encrypted connect
by your client to sTunnel.
If you have anti-virus software configured to intercept your e-mail
traffic, some use transparent proxies but some use opaque proxies. With
opaque proxies (like with sTunnel), the client's config for an account
defined within it points at the AV's proxy, not to the e-mail server.
If you have one of those AV programs, either you disable its opaque
proxy or simply reconfigure the client to point at sTunnel's opaque
proxy; else, you have to figure out how to chain multiple opaque proxies
together (client configured to connect to sTunnel proxy configured to
connect to AV proxy, or maybe client to AV to sTunnel).
Would it make any sense to run an email server on my laptop? That seems
like it would need to be the email endpoint, no? That would mean I'd have
to host the domain name on my laptop, right?
If you have a personal account with your ISP, check their terms of
service. They may not allow Internet-facing servers by their customers.
I know some users that ran afoul of such restrictions when running file
or gaming servers on their PCs at home on a personal-use service tier.
You can run afoul of anti-spam blacklists. You won't be running your
own nameserver so your SMTP server won't have an MX record showing it is
authorized to send from your domain. If you don't register a domain
then your SMTP server will only have an IP address which means no
reverse DNS lookup. Some anti-spam filters don't like non-unique MX
servers, especially when no MX server is listed at a nameserver at the
domain. You will appear a rogue e-mail source. Nowadays many e-mail
providers use DKIM (domain keys), SPF (sender policy framework), or
DMARC to prove who sent a message an you won't have any of that (see
https://wiki.zimbra.com/wiki/Best_Practices_on_Email_Protection:_SPF,_DKIM_and_DMARC).
You will be an unknown source and unacceptable to other SMTP servers.
Why would you add the complexity of a local SMTP server (you'll have to
find one first) when the easiest solution is to change to a different
e-mail client? There are plenty of free ones. Or perhaps you are a fan
of the Red Green Show? Granted using sTunnel smacks of a Rube Goldberg
setup but switching to another e-mail client is a lot easier.