I recently upgraded from a Samsung Galaxy S8 to a Galaxy S10e.  I am now unable to send MMS while on Wifi and they are very slow to send while Wifi is off.  I used the native messages app.  During debugging I switched to Verizon's Messages+ app, and experienced the same issue.  Oddly, I am able to received MMS with no delay.  I believe the underlying issue is that data signal is suddenly weak.  This is occuring in my home where I never had a problem with the Galaxy S8.  The S10e was purchased from Amazon as a refurbished phone.  I moved the sim card over myself (voice and text service work fine so I am confident that the sim card is seated correctly and not damaged)  Has anyone else experienced this?  I am getting close to returning the phone and assuming I got a bad unit, but I'm also wondering if Verizon is throttling my data since I moved the sim card on my own and avoided their "Upgrade fee".  That sounds somewhat paranoid, I know.