T-online.de mail. Office365

This is based on the assumption that only authorized e-mail systems initiate renewed delivery of rejected e-mails.

Higher bounce rates are an indication of outdated e-mail addresses or lack of verification via double opt-in, which we consider to be misuse.

Make sure that your e-mail systems meet these standards.

This includes: ade, adp, app, asp, bas, bat, bhx, cab, ceo, chm, cmd, com, cpl, crt, csr, der, exe, fxp, hlp, hta, iframe, inf, ins, isp, its, js, jse, lnk, mad, maf, mag, mam, mar, mas, mat, mde, mim, msc, msi, msp, mst, ole, pcd, pif, reg, scr, sct, shb, shs, vb, vbe, vbmacros, vbs, vsw, wmd, ws, wsc, wsf, wsh and xxe.

I asked what blacklists are being used, but am not optimistic I will get a response.

If you are using Windows, you can use the command ' tracert mx00.

Such an error should be found in the log of your e-mail system.

Please configure your mail server s so that a new connection is not established for every e-mail, and the number of messages to be transferred via one connection is not restricted unnecessarily. Redirects introduce additional delays before the page can be loaded. You can also reach this person via any of our listed systems. If error messages occur regularly or even permanently, these indicate errors that should be analyzed in more detail urgently. Errors reported to Telekom are dealt with promptly. Telekom does not offer any whitelisting. This procedure has numerous vulnerabilities that cannot be compensated for, including those that are described.
15|5|22