Good evening everyone, I have the following problem: 1-I have only one domain that the customer complains about the message above in the title when replying to any email received in his mailbox. This client normally sends any message if it creates in roundcube, it receives all messages without problems. When he selects a message received with or without attachments, he cannot respond because the Connection Error message appears (Failed to communicate with the server) only for his domain account, the other accounts are all ok. Note I checked the following: In dns administration appears his domain as: local date =yes local mail =no I added his domain in the /etc/virtual/domains file gone local error mail =no and changed to yes But it didn't work can anyone help.