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VRFY/RCPT TO failed on 421 - temp error of the target MTA

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VRFY/RCPT TO failed on 421 - temp error of the target MTA

Renaud-14
Hi there,

On my setup I verify the validity of my email addresses using the VRFY/RCPT TO method.

Today the backend MTA which reply to ASSP for this kind of check got some trouble and replied with a temporary error (421).  

The issue is that ASSP replied with an error 550 to the client MTA which push some confusion because the sender think that the recipient address doesn't exist but it's false.

Moreover I'm pretty sure that ASSP wrote in his cache that the address doesn't existe as well.

It could be more convenient to reply by a 421 in this particularly case don't you ? 

Renaud

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Re: VRFY/RCPT TO failed on 421 - temp error of the target MTA

Thomas Eckardt/eck
'LDAPFail' - controls the reported validy of an address in case of a '4xx' reply of the MTA.
ASSP itself knows only two states of an address - valid or notvalid.
If an address not valid, this is a permanent error.

ASSP offers several mechanism to prevent this case - SPOF,

- ldaplistdb for caching
- LDAP failover hosts
- VRFY failover hosts
- use VRFY as failover for LDAP

Thomas




Von:        Renaud <[hidden email]>
An:        [hidden email]
Datum:        13.05.2017 01:07
Betreff:        [Assp-test] VRFY/RCPT TO failed on 421 - temp error of the target        MTA




Hi there,

On my setup I verify the validity of my email addresses using the VRFY/RCPT TO method.

Today the backend MTA which reply to ASSP for this kind of check got some trouble and replied with a temporary error (421).  

The issue is that ASSP replied with an error 550 to the client MTA which push some confusion because the sender think that the recipient address doesn't exist but it's false.

Moreover I'm pretty sure that ASSP wrote in his cache that the address doesn't existe as well.

It could be more convenient to reply by a 421 in this particularly case don't you ? 

Renaud------------------------------------------------------------------------------
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Re: VRFY/RCPT TO failed on 421 - temp error of the target MTA

Renaud-14
In reply to this post by Renaud-14
Hello Thomas,

2017-05-14 11:34 GMT+02:00 Thomas Eckardt <[hidden email]>:
'LDAPFail' - controls the reported validy of an address in case of a '4xx' reply of the MTA.
ASSP itself knows only two states of an address - valid or notvalid.
If an address not valid, this is a permanent error.


Oki so if the MTA reply by a 421 ASSP get this as an error ? If yes it's what I was looking for.

 

ASSP offers several mechanism to prevent this case - SPOF,

- ldaplistdb for caching
- LDAP failover hosts
- VRFY failover hosts
- use VRFY as failover for LDAP


Today in localdomains I've file:/files/localdomains.txt and inside I've several <domainX> => smtp1:25

If I'd like to add another MTA as failover for VRFY I just have to add a line with <domainX> => smtp2:25 isn't it ?

Cheers,
Renaud

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Re: VRFY/RCPT TO failed on 421 - temp error of the target MTA

Thomas Eckardt/eck
>I just have to add a line with <domainX> => smtp2:25 isn't it ?

NO!

<domainX> => smtp1:25,smtp2:25

Use the syntax: *mydomain.com=>smtp.mydomain.com|other.com=>SSL:mx.other.com:port|other2.com=>mx.other.com:port,mx2.other.com:port to verify the recipient addresses with the SMTP-VRFY (if VRFY is not supported 'MAIL FROM:' and 'RCPT TO:' will be used) command on other SMTP servers.
The entry behind => must be the hostname:port or ip-address:port of the MTA which is used to verify 'RCPT TO' addresses with a VRFY command! If :port is not defined, port :25 or :465 (in case SSL: is defined) will be used. You can use an entry like ALL=>vrfyhost:port to define a VRFY host for all local domain entries that don't have a MTA defined ( better use 
Groups ). Separate multiple VRFY hosts for failover by comma ",". You have to enable the SMTP 'VRFY' command on your MTA - the 'EXPN' command should be enabled! This requires an installed Net::SMTP module in PERL. 

??????????????????????!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Thomas



Von:        Renaud <[hidden email]>
An:        ASSP development mailing list <[hidden email]>
Datum:        15.05.2017 00:04
Betreff:        Re: [Assp-test] VRFY/RCPT TO failed on 421 - temp error of the        target MTA




Hello Thomas,

2017-05-14 11:34 GMT+02:00 Thomas Eckardt <Thomas.Eckardt@...>:
'LDAPFail' - controls the reported validy of an address in case of a '4xx' reply of the MTA.
ASSP itself knows only two states of an address - valid or notvalid.

If an address not valid, this is a permanent error.



Oki so if the MTA reply by a 421 ASSP get this as an error ? If yes it's what I was looking for.

 

ASSP offers several mechanism to prevent this case - SPOF,


- ldaplistdb for caching

- LDAP failover hosts

- VRFY failover hosts

- use VRFY as failover for LDAP



Today in localdomains I've file:/files/localdomains.txt and inside I've several <domainX> => smtp1:25

If I'd like to add another MTA as failover for VRFY I just have to add a line with <domainX> => smtp2:25 isn't it ?

Cheers,
Renaud------------------------------------------------------------------------------
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engaging tech sites, Slashdot.org!
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individual to whom it is addressed.
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