Edit - apologies - I mstakenly said Ipad when it was your Iphone - however they both use the same operating system. The Iphone's smaller screen makes some things appear different, but the underlying systems are exactly the same.
Lets use Thunderbird to see what additional information we can gather as to the problem. If you can receive but not send I'm guessing it could be a 525 VM 304 error - However rather than make assumptions I'd rather see what Thunderbird shows.
Only use Helpful answer if your problems been solved.
Thanks for your help, however I have replicated my Outlook settings (where it works perfectly) into Android account and it doesn't work.
Please start your own thread. This one is about solving issues with APPLE DEVICES not Android devices.
Superuser 2016/17 Use Kudos to say thanks Mark answer as "helpful" only when the problem is solved Please don't send me private messages unless I ask you to. I do not work for VM. The advice I give is based on my best understanding of VM policy and practice. You rely on it at your own risk.