Please bear in mind that the following SMTP servers have reported problems:
29.05.2023, 09:40:55 This is the mail system at host e-university.tu-sofia.bg.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<opetrov@uni-ruse.bg>: host mx2.uni-ruse.bg[91.210.88.19] said: 554 5.7.1 We
did not like your spam. Go away! rspamd.uni-ruse.bg (in reply to end of
DATA command)