Sorry, re-read your question and realise my suggestion would only help you get SASL authentication working.
> On 31 Mar 2021, at 09:19, Jamie Burchell <mail@xxxxxxxxxxxxxxxxx> wrote:
>
> I'm pretty sure I encountered this and needed to yum install cyrus-sasl-plain to resolve it.
>
>> On 29 Mar 2021, at 20:31, Nicolas Kovacs <info@xxxxxxxxxxxxx> wrote:
>>
>> Hi,
>>
>> My main mail server is running CentOS 7 with Postfix and Dovecot.
>>
>> Last week I was surprised to see that Postfix had some troubles on this
>> machine, according to Icinga. I took a peek at the logs:
>>
>> # journalctl -p err
>> Mar 28 04:37:02 sd-151768 postfix/smtpd[2786]: fatal: no SASL authentication
>> mechanisms
>> Mar 28 04:37:02 sd-151768 postfix/smtpd[2788]: fatal: no SASL authentication
>> mechanisms
>> Mar 28 04:37:02 sd-151768 postfix/smtpd[2790]: fatal: no SASL authentication
>> mechanisms
>> Mar 28 04:37:02 sd-151768 postfix/smtpd[2792]: fatal: no SASL authentication
>> mechanisms
>> Mar 28 04:37:02 sd-151768 postfix/smtpd[2794]: fatal: no SASL authentication
>> mechanisms
>> ...
>>
>> And in /var/log/maillog I found a tsunami of these:
>>
>> Mar 28 03:18:33 sd-151768 postfix/smtpd[29589]: warning:
>> unknown[45.227.253.115]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
>> Mar 28 03:18:33 sd-151768 postfix/smtpd[29589]: lost connection after AUTH from
>> unknown[45.227.253.115]
>> Mar 28 03:18:33 sd-151768 postfix/smtpd[29589]: disconnect from
>> unknown[45.227.253.115]
>>
>> My first reaction was to manually ban the IP addresses / networks which caused
>> the flood, using my firewall:
>>
>> # firewall-cmd --permanent --add-rich-rule="rule family='ipv4' source
>> address='45.227.253.0/24' reject"
>> # firewall-cmd --reload
>>
>> I'm already using fail2ban in conjunction with firewalld to prevent brute force
>> SSH attacks.
>>
>> Q: can I use it in a similar configuration to stop Postfix from getting flooded
>> and brought down to its knees?
>>
>> Thanks & cheers from the sunny South of France,
>>
>> Niki
>>
>> --
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>> 7, place de l'église - 30730 Montpezat
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