Issues with Microsoft Outlook 2007

I’ve been using Synesis since way back in 1997—honestly, we’re talking about the days when we were still running on DOS—so I practically have the whole thing memorized by heart.

For a while there, everything was sending perfectly fine through Outlook, but now? Well, I suspect some recent security update has gone and completely thrown a wrench in the works.
I even reached out to Pupill, but unfortunately, they weren't able to offer much help since the headache seems to be rooted in Outlook itself rather than anything involving their specific software...

I had really hoped that someone in this community might have the insight to tell me exactly how to fix this mess...

Hey everyone, I know we’ve all been struggling here, but it turns out the issue was actually with the server itself. 🙄
Basically, they set it up so all our emails go straight to Yahoo because there isn't enough storage space on the server right now. It's just a temporary fix until they expand the capacity. I mean, of course my inbox ran out of room once I opened everything up. 🤦 😬
The plan is to resolve this by configuring the server to send mail directly to our business accounts first, which will then simply forward over to Yahoo.
As for attachments, everything seems to be attaching correctly now. Perhaps that was just an isolated glitch? I'll keep an eye on things and see how it goes.
Thanks to everyone for the help. I know I wasn't exactly clear when I first described what was happening, but computers aren't exactly my specialty. 🙈