There is a fragment of text (in $CVS/mailman/messages/ru/LC_MESSAGES):
,--- [ mailman.po ] --- | #: Mailman/Deliverer.py:158 | msgid "" | "%(address)s was invited to a different mailing\n" | "list, but in a deliberate malicious attempt they tried to confirm the\n" | "invitation to your list. We just thought you'd like to know. No further\n" | "action by you is required." `----[ ] ---
Is this correct: ``address was invited'' and ``they tried''? ^^^- singular ^^^^- plural
This is not technically correct English, but it's a very common usage.
Since there is no gender-neutral way in English to refer to a person whose gender is unknown (in this case, the owner of the email address) the word "they" in a singular sense is often used for this purpose.
"He or she" (which is more correct) sounds awkward in many cases, and the singular pronoun "it" is not used to refer to people.
To be more correct, "he or she" should probably be used in the original English above, but the original sentence is completely understandable to this native English speaker.
You can translate it as a gender-neutral singular pronoun like "it" if your language uses that for people, or use the equivalent of "he or she".