I tried to move off fastmail back to gmail last year because I lost a job opportunity due to a random fastmail-origin email i sent getting blocked by my intervi

I tried to move off fastmail back to gmail last year because I lost a job opportunity due to a random fastmail-origin email i sent getting blocked by my interviewer's google mail. the first three went through fine, it was only the fourth one that didn't make it. they thought i ghosted and had already chosen another candidate because of it. ultimately i didn't make the move because email is unusable without custom aliases i can completely bounce email from. but i think i might attempt again, but again I recently found myself insanely paranoid about my interviewing situation and had to make the awkward transitioning to my gmail account and explain why to my interviewer