Can no longer send mail with mutt email client: Sender address rejected

[liberator]

I've been sending mail with mutt email client, and I sent a few dozen test messages yesterday. Than all of a sudden I started getting the following error (I replaced my email address with "mymail") :
SMTP session failed: 554 5.7.1 [email protected]: Sender address rejected: Access denied

I did not change any mutt settings before this started happening and it is still happening today. I can still send email through webmail however.

Here is my .muttrc file where I replaced with my email address with "mymail", and my password with "mypassword":

    set from = "[email protected]"
    set realname = "mymail"
    set imap_user = "[email protected]"
    set imap_pass = "mypassword"
    set folder = "imaps://imap.vivaldi.net:993"
    set spoolfile = "+inbox"
    set postponed ="+drafts"
    set header_cache =~/.mutt/cache/headers
    set message_cachedir =~/.mutt/cache/bodies
    set certificate_file =~/.mutt/certificates
    set smtp_url = "smtp://[email protected]:587/"
    set smtp_pass = "mypassword"
    set move = no
    set imap_keepalive = 900

I can't figure out what is happening.

[gmg]

@liberator Why is the imap_user vivaldi.com and not vivaldi.net? Was that just a typo here?

[liberator]

Yes, that was a typo. I've corrected it. It was set that way before and after the issue began. I am able to receive mail with it set either way. I still can't send mail.

[thomasp]

Please contact the support team via the button at the bottom of https://help.vivaldi.com/services/webmail/troubleshooting-webmail-issues/