From Newsgroup: comp.mail.sendmail

For the last 25 years, I've run sendmail, relaying my email through
my ISP using the SMART_HOST sendmail.mc option.

Over the weekend, my ISP introduced changes to their smtp service to
require a login with password. Consequently, all my outbound mail now
rejects with a
451 4.3.5 <recipient email address>: Recipient address rejected: Server configuration problem

Does anyone have any advice as to how I can configure sendmail 8.15 to
send an appropriate userid (my ISP email address) and password?

Any help or advice would be greatly appreciated
--
Lew Pitcher
"In Skills We Trust"
Not LLM output - I'm just like this.
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From Newsgroup: comp.mail.sendmail

On 01.09.2025 18:12 Uhr Lew Pitcher wrote:

Does anyone have any advice as to how I can configure sendmail 8.15 to
send an appropriate userid (my ISP email address) and password?

https://unix.stackexchange.com/questions/204299/centos-sendmail-smtp-smarthost-with-authentication
--
kind regards
Marco

Send spam to 1756743171muell@stinkedores.dorfdsl.de

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From Newsgroup: comp.mail.sendmail

Thanks, Marco

That looks like it will work for me. I'll give it a try.

On Mon, 01 Sep 2025 20:39:43 +0200, Marco Moock wrote:

On 01.09.2025 18:12 Uhr Lew Pitcher wrote:

Does anyone have any advice as to how I can configure sendmail 8.15 to
send an appropriate userid (my ISP email address) and password?

https://unix.stackexchange.com/questions/204299/centos-sendmail-smtp-smarthost-with-authentication

--
Lew Pitcher
"In Skills We Trust"
Not LLM output - I'm just like this.
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From Newsgroup: comp.mail.sendmail

Thanks, again, Marco

On Mon, 01 Sep 2025 20:39:43 +0200, Marco Moock wrote:

On 01.09.2025 18:12 Uhr Lew Pitcher wrote:

Does anyone have any advice as to how I can configure sendmail 8.15 to
send an appropriate userid (my ISP email address) and password?

https://unix.stackexchange.com/questions/204299/centos-sendmail-smtp-smarthost-with-authentication

This (and a couple of other changes that this lead to) fixed my problem.

Thanks again for the assistance.
--
Lew Pitcher
"In Skills We Trust"
Not LLM output - I'm just like this.
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From Newsgroup: comp.mail.sendmail

On Mon, 01 Sep 2025 23:18:42 +0000, Lew Pitcher wrote:

Thanks, again, Marco

On Mon, 01 Sep 2025 20:39:43 +0200, Marco Moock wrote:

On 01.09.2025 18:12 Uhr Lew Pitcher wrote:

Does anyone have any advice as to how I can configure sendmail 8.15 to
send an appropriate userid (my ISP email address) and password?

https://unix.stackexchange.com/questions/204299/centos-sendmail-smtp-smarthost-with-authentication

This (and a couple of other changes that this lead to) fixed my problem.

Thanks again for the assistance.

So, I have had a stable outbound email connection for a couple of days now,
and I thought that I'd summarize the changes I had to make to my sendmail.mc
to make this work.

So, for the past 15 years, I've successfully relayed my outbound email through my ISP's smtp server using the sendmail SMART_HOST configuration option. /Just/ the SMART_HOST option, and no other changes. This weekend, I lost that ability.

I followed up with my ISP's help desk, but (because of the statutory holiday) they couldn't answer the particulars of my question ("How do I connect?").

They, while admitting to having made changes "to authentication", could not tell
me what the connection requirements had changed to. Some googling pulled up a "help" document from their website (not directly linked to any of their public pages, so, effectively buried) that suggested their smtp connection
a) now resided on a different port, and
b) required a username and password

Hence, my questions here.

After a few hours of research and testing, I came up with the following:
1) To address the port change from the hidden documentation, I added
define(`RELAY_MAILER_ARGS', `TCP $h 587')dnl
to my sendmail.mc
2) To address the authentication issue, I added
AuthInfo:relayhost.dns.name "U:USERNAME" "P:PASSWORD" "M:LOGIN PLAIN"
(substituting the appropriate ISP webmail values for USERNAME and PASSWORD)
to my /etc/mail/access file, and rebuilt the /etc/mail/access.db file.
3) I restarted my sendmail installation.

It worked. And now I'm back in business.


Addendum:
Late yesterday evening, my ISP left me a voicemail regarding my initial problem. Their answer was "It's fixed. You should have no trouble now."
And, yes, my original, just plain SMART_HOST, configuration works fine.
But, I'm sticking with the authenticated version, just in case they
drop the unauthenticated connection again.


Thanks again to Marco for the push in the right direction, and to the
authors of the (many) webpages and documents I referenced to find the
clues to my fix.
--
Lew Pitcher
"In Skills We Trust"
Not LLM output - I'm just like this.
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From Newsgroup: comp.mail.sendmail

On 03/09/2025 13:52, Lew Pitcher wrote:

2) To address the authentication issue, I added
AuthInfo:relayhost.dns.name "U:USERNAME" "P:PASSWORD" "M:LOGIN PLAIN"
(substituting the appropriate ISP webmail values for USERNAME and PASSWORD)
to my /etc/mail/access file, and rebuilt the /etc/mail/access.db file.

Thanks for sharing your answer Lew

As I hadn't come across "M:LOGIN PLAIN" before I had a poke around
sendmail 8.18.1 source. There I found some information on SMTP
AUTHENTICATION in the cf/README file which includes

----
The RHS for an AuthInfo: entry in the access map should consists of a
list of tokens, each of which has the form: "TDstring" (including
the quotes). T is a tag which describes the item, D is a delimiter,
either ':' for simple text or '=' for a base64 encoded string.
Valid values for the tag are:

U user (authorization) id
I authentication id
P password
R realm
M list of mechanisms delimited by spaces

Example entries are:

AuthInfo:other.dom "U:user" "I:user" "P:secret" "R:other.dom" "M:DIGEST-MD5" AuthInfo:host.more.dom "U:user" "P=c2VjcmV0"

User id or authentication id must exist as well as the password. All
other entries have default values. If one of user or authentication
id is missing, the existing value is used for the missing item.
If "R:" is not specified, realm defaults to $j. The list of mechanisms defaults to those specified by AuthMechanisms.

Since this map contains sensitive information, either the access
map must be unreadable by everyone but root (or the trusted user)
or FEATURE(`authinfo') must be used which provides a separate map.
Notice: It is not checked whether the map is actually
group/world-unreadable, this is left to the user.
----

I also found the following pages helpful: https://www.sendmail.org/~ca/email/auth.html https://www.samlogic.net/articles/smtp-commands-reference-auth.htm

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