Outgoing emails from Outlook client failing to reach Gmail accounts

[#1]

I had reports that my sent emails hadn't been received, and had no failure or bounce back from heir server or Plusnet. I tried my 2 personal Gmail accounts and no failure returned to my client, but not received at those accounts. I logged into Webmail and forwarded emails to those Gmail accounts and they failed with:

Message not sent. Server replied:

Requested action not taken: mailbox unavailable
550 <{mailbox}@{username}.plus.com> invalid address '{mailbox}@{username}.plus.com'

I have forwarded emails to these accounts successfully only a week ago.

Any ideas where to start?

[#2]

PlusNet is blocked on many email servers; perhaps use Microsoft server, or M/Soft Exchange.

[#3]

Hi Gel,

many thanks for your input, much appreciated.

I do have several Gmail addresses that I successfully send to regularly, and I have sent to my own Gmail addresses previously and recently, but they are failing (mostly) now. I have had, randomly, some getting through from my Outlook client, but across 24 Hours, so very slow, but not every email gets through and my webmail doesn't work at all now, to those addresses anyway. I noticed that the webmail client has changed to something called 'Squirrel' and it isn't a fully functional app. Is something going on?

[#4]

@ChrisA999 

Are you still encountering this issue?

Sender Domain Rejected (black listed by local policy)

This issue can report as server error 550. It typically arises where a user's email address has been abused for the purposes of sending spam emails. It has nothing to do with server settings etc.

This requires intervention by staff to determine the cause of the problem and to issue advice to check your system for viruses and malware. Only after your system(s) have been affirmed to be clean can the black listing be lifted. As a precaution, you should change the password on the affected email address.

Add your details to this thread - Cannot Send Emails and send a PM to @Leanne_T

Webmail has not changed- you can still use the RoundCube webmail client or Basic webmail which is indeed Squirrel.  In some ways it is better than roundcube.

[#5]

Many thanks Townman. I haven't checked it for a week, so I'll do so later to confirm (work at the mo). I'll let you know...