If you're unable to send email through your mail client at the moment, and are receiving a message that says Authentication Credentials Invalid (VM300) could you please try changing your password for that address in My Virgin Media.
We're keen to see if this helps at all after we've carried out some work on the problem. Once you've updated the password, you'll need to update it in your mail client as well.
If the password change DOESN'T work, please post below to let us know. Please provide the following:
Error Message seen in your mail client
Timestamp of the error
If your issue isn't related to a password error when sending email, please post a new thread so the Forum Team can look into things for you.
The first post in this thread also asked if you provide a time of password change so the team can track down the issue. Can you help on this as well please. The error message looks typical of the problem of failing SMTP authentication. Worried though that you are not seeing a VM300 code as well in the message. The VM Forum Team will pick this up shortly and get a look taken at your account.
As a Very Insightful Person, I'm here to share my knowledge. I don't work for Virgin Media.
I've just changed the password again at 18.55 but now getting "We couldn't log on to the incoming (IMAP) server. Please check your email address and password and try again" when adding the account in Outlook 2016.
This is different to what I'm getting when adding my original (primary) email address. As mentioned earlier I get the SMTP error.