Hi, Need your support here.I am reaching out to you regarding an issue
with the t-online.de domain that we are experiencing. We have a
relatively low delivery rate of 86,5% for one the recent campaigns (96
out of 710 have been blocked). Almost half of the undelivered emails
have been rejected with the error message: 554 IP=a.b.c.d - A problem
occurred. (Ask your postmaster for help or to contact ...@... to
clarify). The common denominator of these emails was the t-online.de
domain, so we contact...