Hello @EliseL ,
No email program would immediately trash a received email that it thought was suspicious, it would simply bounce it back or put into junk/spam. The only way something like that happens is if there's a setting or more likely a filter in that particular contact's email program. For example, I have several filters in my work email set to capture particular subject lines or contexts to automatically filter into trash. Successful delivery, but it stays out of my inbox so I don't have to manually delete something that no longer pertains to me or I'm never interested in.
Ultimately your contact will want to check their current filters or email settings, to see if they have anything that would result in emails coming from our domains or from your email address being moved into trash after a successful delivery. They (or their IT team if applicable) may need to look into safelisting your address or our domains.