SMTP 550 Error in Roundcube — “Failed to set sender” intermittently

[GustavoMS]

Hi everyone,


I’m having an intermittent issue when sending emails through Roundcube.

Sometimes, when sending a message, the following error pops up in the webmail interface:


An error occurred!
SMTP Error (550): Failed to set sender "" (Account ******@****** can not send emails from .)


Checking the Exim logs, I found entries like these:


2025-08-11 08:53:01 H=localhost (******) [127.0.0.1] rejected MAIL <>: Account ******@****** can not send emails from .
2025-08-11 10:20:38 H=localhost (******) [127.0.0.1] rejected MAIL <>: Account ******@****** can not send emails from .
2025-08-11 10:26:42 H=localhost (******) [127.0.0.1] rejected MAIL <>: Account ******@****** can not send emails from .

Additional notes:

• It happens to different users at different times (not always the same account).
• From what I can see, the sender field is empty ("") in these cases.
• The issue started in the last two weeks and happens to all users.

Has anyone experienced this before or knows what could be causing it?


Thanks in advance!

 

[zEitEr]

Hello,

It might be related to: https://docs.directadmin.com/changelog/version-1.680.html-sender-address-spoofing-protection

Try and disable the SPOOFING protection and test sending in RoundCube.

 

[GustavoMS]

Let's test it.

Thanks for the quick response.