The platform web browser on Android does not allow tel: or mailto: links to work correctly in any case. In order to compose a mail message to an address on this platform you need to use other platform mechanisms.
Attempting to launch URLs on Android causes http:// to be placed before the string that is given. This causes issues when using commands such as mailto: and tel: which do not work properly when this is added.
This also occurs in 4.17 and 4.18
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-59099 in the post.