I can’t say anything with regard to whether LON1 is the cause of the issue, but you might want to look into setting up a well-known SMTP relay to prevent your emails from being marked as spam. If your daily outgoing email count is no more than about 300, most services offer this free of charge, but if you send emails more frequently than this, there is usually a fee. Such services include:

• SendInBlue (https://www.sendinblue.com/pricing/)
• Amazon SES (https://aws.amazon.com/ses/pricing/)
• Postmark (https://postmarkapp.com/pricing)

If you have any further questions, feel free to ask, and I’ll try to assist as best as I can.

I suggest you to check your account first if you are not able to receive any mail from BT Mail may be something is missing in your account which cause the reason of blocking BT mail. If still you are facing this issue then contact BT Mail Support Team Once.