Solved: Mail not sending (sort of)

Continuing the discussion from SMTP Error (530): Failed to set sender "" (5.7.0 Must issue a STARTTLS command first):


  1. I log into my Roundcube account
  2. I click compose to compose a message
  3. I enter the email address into the To field
  4. I enter a subject into the Subject field
  5. I enter a message in the body field
  6. I click the Send button
  7. I get an error message about the spelling check

and nothing happens. Usually, I see a message that says the message went through and the window closes. This time, the window remains open.

I checked and sometimes the message does actually go through anyway. How strange.

It works now. Not sure why.

Hello, how did you solve this problem?
I’m having the same problem too.
find attached for the error message.

“SMTP error (450); failed to add recipient (4.1.8>: Sender address rejected: Domain not found)”