We have replaced fetchmail to wsgetmail.
WSgetmail starts procmail to push the e-mails to rt-mailgate.
It worked great until the external script occasionaly executed by procmail returned an error.
After the analysis, it turned out that procmail showed signs “^M” (carriage return) in the fields: FROM, TO, SUBJECT.
Wsgetmail adds ^M on the end of these fields each time.