I have had the same issue all weekend, and this evening. This is on my iPad, iPhone and using Mozilla Thinderbird on the PC. They sit in the outbox on the iPhone and iPad then says it cannot send mail. It just sits in the outbox and might send when it feels like it.
Emails sent today while at work, and I had no problem sending using webmail on the website all weekend.
This appears to be a VirginMedia issue looking at the threads and people replying now.
My missus just tried to send an email from her address and it wouldn’t send either, from her iPad and iPhone.
Thanks for reaching out to us in our community and welcome back, I am sorry you are having issues with your emails, have you tried using different browsers to see if this helps or a different none apple device other than the PC ?