Hi @MG1 ,
Thanks for raising this to us, we're sad to know that you're having issues sending emails. Here is an article that you may find helpful.
Please see the link, Cannot Send Email Rejected by the Server/Banned from using SMTP
Let us know how it will go.
The last couple of days I am unable to send email replies to my customers for our business. See attached photo for what I keep receiving after I send the email