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 toAnswerHub just mention UE-59099 in the post.