Hello,
Any filtering software that might be catching such things would not be on the endpoint that is the machine I use for the email address in question, but rather at the hosting facility. Ie, I rent a rack and know that certain things do get filtered for I’ve had this issue with clients in the past. If I knew the originating email address’s domain I could get it whitelisted, but this wouldn’t be possible to know beforehand obviously =]
Perhaps you can advise further so I can whitelist?
Thank you