The fact that this so called developer doesn't understand the difference between a sender and a receiver of email makes me think there are other things in the CV that caused them to not be hired.
And it's not like "email" is some esoteric thing he's only now come into contact with.
For example, don't say "GMail". This is about email. To misquote Babbage: "I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a conclusion".
This conclusion screams of not being able to understand the logical effect of a known fact. I wouldn't want this person troubleshooting anything, for example.
And I didn't see many comments about the rest of his statements. It's a mess. He seems somewhat angry at GMail's suggestions (this would be on the sender side) because sometimes he doesn't want to say what GMail suggests. Again… confusion of ideas.
Actually, now that I think about it I'm seriously suspecting this was written by a bot. More articles than you'd expect are written by bots, and this is close enough to making sense (on multiple points), but without an actual logical point, that it's a possibility.
I would add that I think it's a bit fickle and unkind for internet strangers to pass judgement on a person's ability to do their job based on a post like this. This individual did not ask for our opinion on their ability to do a job, but instead gave (a useful) warning about how the gmail client handles CVs.
That's one way to see it. To me it was about as coherent and thought through as someone yelling and on the corner about 5G towers causing coronavirus.