Outgoing mail blocked intermittently

[NETLINK]

Hi,

Every so often, outgoing mail gets blocked on my cPanel server. All messages are bounced back with following error:

550-Please turn on SMTP Authentication in your mail client.
550-xxxxxx.com [xx.xxx.xxx.xx]:53492 is not permitted to relay
550 through this server without authentication.

When I restart the CSF firewall, it works again, but the same issue could occur several hours later, sometimes, days or weeks later. This started happening a few months ago.

I haven't been able to figure out why. Any help would be appreciated.

[peopleinside]

Hi, are you sure this issue is caused from CSF ?
I think the issue is not CSF ... relay email issue ... i believe the cause is not the firewall.

[NETLINK]

Hi! I am fairly sure, yes. This happens with all outgoing. Relay domains, local domains, even mails configured to go out using remote SMTP servers.

[peopleinside]

Hi NETLINK, in this case i cannot help.
Check in the CSF you have allowed port for outgoing email. Usually the relay issue is not related to CSF from what i know about mail server and personal past experience with relay issue.

Be sure to authenticate outgoing email.
Try to search the error on Google: "is not permitted to relay"

[NETLINK]

Hi NETLINK, in this case i cannot help.
Check in the CSF you have allowed port for outgoing email. Usually the relay issue is not related to CSF from what i know about mail server and personal past experience with relay issue.

Be sure to authenticate outgoing email.
Try to search the error on Google: "is not permitted to relay"

Thank you! No worries. I've tried all this. Authentication is working. This starts happening randomly to ALL mail. Mail sent by users, mail that's relayed, system mail. Nothing goes out until I restart CSF. Right now, for example, everything is working fine. But the problem can come back at any time.

[peopleinside]

This issue is present when email are sent by PHP, client email or web interface?
Have also tested (when you have this issue) if each (webmail, client, PHP) are affected from the same issue?

Other suggestion is to check email logs when you see the issue is present.
I am just a CSF user and a "very small VPS Manager" for personal use so i am just try to share my little experience. I use CSF and usually with Exim and Dovecot i do not see this issue.

I can remember in the past i had the relay issue but in my case was related to exim configuration. I can remember was not easy to fix but with time i was able to solve by doing search on the web about the error and the email system used ( Exim and Dovecot).

Hope you can solve soon.

[te0x]

We also have a issue that could be similar.
Even if an IP is in the allow list, it is blocked after some SMTP AUTH failure

Oct 8 08:47:59 srv1 lfd[3387]: *Error*: csf output: deny failed: 94.101.xx.xx is in the allow file /etc/csf/csf.allow

Oct 8 08:47:59 srv1 lfd[3387]: (smtpauth) Failed SMTP AUTH login from 94.101.xx.xx (IT/Italy/host7-....): 5 in the last 3600 secs - *Blocked in csf* [LF_SMTPAUTH]

It seem that the check order is inverted and even if a first test do not let the firewall block, a second one block it.

THanks for any help.

Regards
Te0x

[peopleinside]

Hi te0x , thanks for the update message and to add you on this discussion.
From your message logs seems an issue with CSF but in this case i am not able to help you. I am not very expert of CSF... maybe i found right settings to work on my server ... i am not sure if in this forum an official support is given... seems not... by looking at the other topics... seems a forum between user under CSF section.