Question: I tried multiple combinations you have suggested on your Earthlink setting page, but nothing works.
Please Please Please - help with with settings that you can check yourself on your Mac first.
I used your MaxBulk (paid version 8.5.4US) for many years and now my business stopped...
Answer: If you look at your connection log you will see what the error is:
 5/3 13:50:10 > AUTH PLAIN Mipco **********
504 5.3.3 AUTH mechanism PLAIN not available
Just set the login scheme to LOGIN instead of PLAIN. It is a pull-down menu next to the authentication setting. When connecting your server sends some welcome text, in that text, you can see what it supports, in this case, it supports LOGIN and CRAM-MD5.
MaxBulk Mailer is a full-featured and easy-to-use bulk mailer and mail-merge software for macOS and Windows that allows you to send out customized press releases, prices lists, newsletters and any kind of text or HTML documents to your customers or contacts.
MaxBulk Mailer is fast, fully customizable and very easy to use. MaxBulk Mailer handles plain text, HTML and rich text documents and gives full support for attachments. With MaxBulk Mailer you will create, manage and send your own powerful, personalized marketing message to your customers and potential customers.
Thanks to its advanced mail-merge and conditional functions you can send highly customized messages and get the best results of your campaigns. You also have support for international characters, a straightforward account manager with support for all type of authentication schemes including SSL, a complete and versatile list manager, support for importation from a wide range of sources including from remote mySQL and postgreSQL databases.
MaxBulk Mailer is a software tool that you purchase once, no need to pay on a per-email basis to submission services!