Roundcube not sending mail when send button is pressed

[jimmyeao]

So i have set up Vesta, fixed all the issues in MySQL it leaves, configured Dovecote and created a mailbox.
DNS(MX) records are up to date and I can receive mail.
If I try and send mail, when I click the 'Send' button, nothing happens. I have debug logging on, and nothing..
Using Chrome as the browser, but also the same issue in Edge and IE

Interestingly, if I omit a subject, a pop up prompts me for one, and when I click Send on that box I see a message in the bottom right hand corner saying sending. ALthough the message never actually seems to go anywhere, I do see some entries in exim4.log saying 'Frozen Messaage'
Mxtoolbox shows no serious issues other than no PTR record (I am using virtual hosts on a single ip, not sure of the best way to handle this yet)

Any ideas?

[jimmyeao]

Just ot add to this, I can connect to my mail server from a client (outlook) and send/receive emails just fine (via imap)
It just seems that there is an issue with the roundcube installation