We're expericiencing issues with the "send mail" feature. In fact, when we try to send mail manually (with a defect for example), we have the current error (automails don't work too) :
Messages: Failed to mail the specified entities; Failed to mail the specified entities; Failed to send mail to 'email@example.com' ; Failed to send the message via mail server 'mailhost.der.edf.fr'; Could not connect to SMTP host: mailhost.der.edf.fr, port: 25, response: 421; Could not connect to SMTP host: mailhost.der.edf.fr, port: 25, response: 421;
On the site Administration, I've tried to see the parameters and the SMTP server is correct. The test mail function works (mail is sent and received correctly!!). I tried to had "FROM_EMAIL_ADRESS" in site configuration tab, but it didn't help... We've tried to desactivate the antivirus on a final user computer, but it didn't work.
Do someone have any idea where does this issue come from and where I can search to solve it ?
From your description, the SMTP errors are very similar to a problem we had after a virtual server move. The IP address of the the app server had changed as well as the need to move to a new SMTP array. The significant difference with your issue is that the test mail function worked. If you have not done so, talk to server engineering team and verify the SMPT setup is accurate and as expected in QC. This may be the root cause and not a Site Admin QC issue that you can fix.