Mailing List Archive: error 421 on a new exim4 server

error 421 on a new exim4 server

Jan 8, 2021, 5:11 AM

Post #1 of 5 (494 views)

Hello everyone,

I'm a newbie and currently my goal is just to set a server with the
default Debian config file and the bare minimum modifications to It
necessary to make It work. I tested my email server and domain with
various web tools, everything seems fine, and my ip and domain aren't
blacklisted anywhere.

My problem now is that I noticed that a specific server,
smtp.tiscali.it, is not reachable from my server on his port 25. It's
reachable on port 465, I've verified that with telnet. I tried to send a
few emails yesterday, and after a while they blocked me. The first
emails I sent on that server weren't signed with dkim, and maybe this is
the reason why they blocked my ip on port 25. Now I see on my logs that
the last email is still frozen, and from time to time my server tries to
send it, but I always receive the error 421.

Could you give me some advice, some documentation that I could use to
fix or better understand this please?

PS

Do you think It's still worth reading the book "The Exim smtp Mail
server" by Philip Hazel?

thanks

Alessandro

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Re: error 421 on a new exim4 server [ In reply to ]

exim-users at exim

Jan 8, 2021, 8:01 AM

Post #2 of 5 (494 views)

Permalink

On 08/01/2021 13:11, Ale via Exim-users wrote:
> Do you think It's still worth reading the book "The Exim smtp Mail server" by Philip Hazel?

It's an excellent resource, especially if you learn best
from dead-tree format information. The basic structure
and operation of Exim is unchanged from when it was written.

You'd need to supplement it with the current online documentation
to check for changes since the book was written, for new
features and for esoteric details.

Or, you could just read the online docs end-to-end.
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Cheers,
Jeremy

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Re: error 421 on a new exim4 server [ In reply to ]

exim-users at exim

Jan 8, 2021, 8:03 AM

Post #3 of 5 (494 views)

Permalink

Am 08.01.21 um 14:11 schrieb Ale via Exim-users:

> Could you give me some advice, some documentation that I could use to
> fix or better understand this please?

Do you want to use smtp.tiscali.it as a relay for sending mails? Port
465 would then be the way to go as it is preferred over port 25 for
relaying mails. Don't forget to include client authentication.

If you want to send mails to users within the tiscali.it domain you're
mistaken - their mx servers are not "smtp.tiscali.it". You can check for
them with "dig".

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Re: error 421 on a new exim4 server [ In reply to ]

exim-users at exim

Jan 8, 2021, 8:05 AM

Post #4 of 5 (494 views)

Permalink

Hi,

Ale via Exim-users <exim-users@exim.org> (Fr 08 Jan 2021 14:11:14 CET):
> I'm a newbie and currently my goal is just to set a server with the default
> Debian config file and the bare minimum modifications to It necessary to
> make It work. I tested my email server and domain with various web tools,
> everything seems fine, and my ip and domain aren't blacklisted anywhere.
>
> My problem now is that I noticed that a specific server, smtp.tiscali.it, is
> not reachable from my server on his port 25. It's reachable on port 465,

I've daubt if this is related to you. For me it is unreachable too.
Except for Port 465.

> I've verified that with telnet. I tried to send a few emails yesterday, and
> after a while they blocked me. The first emails I sent on that server
> weren't signed with dkim, and maybe this is the reason why they blocked my
> ip on port 25. Now I see on my logs that the last email is still frozen, and
> from time to time my server tries to send it, but I always receive the error
> 421.

Do you have a proof of successful delivery to their port 25?

> Could you give me some advice, some documentation that I could use to fix or
> better understand this please?

I believe, the mentioned server is simply not built to accept mails on
port 25, but should probably act as a "submission host" for tiscali customers
only.

> Do you think It's still worth reading the book "The Exim smtp Mail server"
> by Philip Hazel?

Definitly.

Best regards from Dresden/Germany
Viele Grüße aus Dresden
Heiko Schlittermann
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Re: error 421 on a new exim4 server [ In reply to ]

exim-users at exim

Jan 8, 2021, 9:25 AM

Post #5 of 5 (494 views)

Permalink

I admit that I did a bit of confusion. I tested their server with an
email I created with them, and once and without authentication.

Anyway now I tried to telnet the port 25 of their mx domains and It's
reachable but I don't receive the message "220 ...",and then they close
the connection after I digit "HELO myddnsdomain".

This is one reason I should read that book ;)

Il 08/01/21 17:03, Kai Bojens via Exim-users ha scritto:
> Am 08.01.21 um 14:11 schrieb Ale via Exim-users:
>
>> Could you give me some advice, some documentation that I could use to
>> fix or better understand this please?
>
> Do you want to use smtp.tiscali.it as a relay for sending mails? Port
> 465 would then be the way to go as it is preferred over port 25 for
> relaying mails. Don't forget to include client authentication.
>
> If you want to send mails to users within the tiscali.it domain you're
> mistaken - their mx servers are not "smtp.tiscali.it". You can check
> for them with "dig".
>

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