Sam Vimes
Moderator
My email is a stand alone third party provider and not associated with my broadband provider or any browser. A hang over from when I was working. I will contact the mail provider to find out if there is a reason for being constantly blacklisted.
In addition, although I have an email address set up as the main default email address in Outlook when replying or creating a new email it uses the secondary email address.
I too have my own domain name and email provider, using IONOS. They like a lot of other providers use blacklists known as SPF records to prevent spam being sent in bulk. Just occassionally they would prevent some of my emails being sent to anyone with a BTINTERNET.COM address because of problems with the records. Seems to have been ok for the last couple of years though.
You have the option when setting up your email accounts in Outlook to specify which one is your default.