Invalid response code received from server

[pixel]

hello


some users if tried to send an email to one domain (testdomain.com) through webmail
they got this error

There was an error sending your message: unable to add recipient [[email protected]]: Invalid response code received from server


please help

 

[Amin Taheri]

This is not an announcement, if your looking for help please post in the correct spot.

 

[MTyagi]

please help me i'm getting below msg when try to send mail through Webmail (Horde).

There was an error sending your message: unable to add recipient [[email protected]]: Invalid response code received from server

 

[sads]

unable to add recipient [[email protected]]: Invalid response code received from server
I used Plesk 9.0.1
Horde imp-h3-4.1.6 how can I fix this error?

Logs in TMP Folder

an 09 11:03:04 HORDE [error] [imp] unable to add recipient [[email protected]]: Invalid response code received from server [on line 1059 of "C:\inetpub\vhosts\webmail\horde\imp\compose.php"]