Funky messages in my inbox when checking mail through iPhone?

A few times recently when I have checked for gmail on my iPhone, I’ve gotten really weird messages. Several messages come up that say “no sender” and there is no message and a date like 12/31/69. I cannot go in to them to delete them. Sometimes it shows that there are 500 of these. Anyone have the same issue or know what to do about it? It doesn’t as yet seem to jeopardize real messages coming through, but it is worrisome.