messages bouncing

[DebbieW]

I have two btinternet.com email addresses, one for work and one for home, and both have the same issue.  Messages are being returned with the following message: 550 spam, or phishing or malware.  Please check or edit your message and try sending it again. (6-1-3-2) ID (6139429002966036)

We have malware checkers and the messages are not phishing. I've tried resending but even if I reword them first they bounce again. 

These are routine messages, often sent to people in my address book or in response to emails to me. Some are using template replies I've been using for months. Some are short and some are long. Some include links, others do not.  I've had three today and at least one a day in the last week. It's getting really annoying. Any suggestions?

[stevebrass]

Are you using an app/client to send emails? if so which one(s) and what devices?

[DebbieW]

I'm using Outlook on a desk top PC. I have other email addresses connected to work websites that are working perfectly, also going through Outlook. So I'm guessing the problem is not there. 

[stevebrass]

Have you checked the outgoing mail server settings for the BT addresses?

Are they as shown here https://www.bt.com/help/email/manage-email-account/manual-settings/what-are-the-settings-for-outgoin...

[DebbieW]

Sorry for delay in getting back to you. As far as I can see all the settings are on the correct options.  I feel I am tempting fate writing this but the problem has not recurred yesterday or today, after being every day for two or three weeks. Fingers crossed whatever it was has sorted itself.