"Fixes" I've found on earlier threads do not resolve the issue. Details follow.
iPhone 11 running 14.7.1 cannot send images via MMS to Android phones. When sending an image, with or without a caption/text, a progress bar at the top slowly progresses and eventually pauses for a period near completion - then ultimately displays a red exclamation mark and "Not Delivered". This did not start after any particular update or other change that I am aware of. It has been occurring at least intermittently for an extended period of time, but if I retried a few times it used to eventually send. Now it is EVERY time I try and no matter how many times I retry it will not send.
Cellular Data is set to "Roaming On". I have tried it with and without Wifi being turned on/connected. In Messages app, "MMS Messaging" is turned on. I have tried resetting network settings, and also retried resetting "all" settings. The phone has been turned off and on multiple times with no improvement. The problem occurs in any geographic area - so it's not a single bad signal area. The problem occurs with any Android user and has been replicated with different photos, different time of day, and tried both with and without accompanying text.
How about some instructions on how to do that? If I click on your profile name, then 'view profile', then 'send message', it just brings up a screen that says 'Private Messages' but does not have a way to actually send one. I'm using the current version of Safari, really doesn't seem like this should require me to use a different browser to get it to work.