...
wie vermutet werden die Emails von T-Online geblockt
habe eine Beschwerde aufgegeben, mit wenig Hoffnung auf Erfolg
Provider wechseln 
I inquired about this problem this morning, and it turns out this has been an
issue also for other users from Germany.
https://www.bricklink.com/message.asp?ID=1057313
We have already contacted t-online about this issue, and apparently it can take
some time for the matter to be resolved. In the meantime, please contact t-online
directly yourself and ask them to unblock BrickLink.com emails.
Like I mentioned to you before, I am having a similar issue between my personal
account (mc.net) and gmx.de. It's very frustrating, since for the first time
in memory I can't send attachments to my fellow Lego fans in Germany.
Please let me know of any developments on your end. Thanks!
