One more thing:
Issue
Email is not sent because of failed authentication:
Reason
This error is caused by your SMTP server - it uses different type of authentication method.
By default AquaMail is using the correct method for the most popular Web mail providers.
Solution
You can manually setup another authentication method in your Account Configuration:
> long press on Account name > Account setup > MANUEL > NEXT > in "Edit an account: Outgoing server" go to "Authentication" - you can choose a specific authentication method which should be used during authentication to SMTP server:
° "Choose automatically" (usually as default)
° "Do not login"
° "SASL CRAM-MD5"
° "SASL LOGIN"
° "SASL PLAIN"
To explain it more, login to SMTP server can be authenticated by different methods: CRAM-MD5, DIGEST-MD5, LOGIN, PLAIN, ... (some others)
What is SASL ?
Simple Authentication and Security Layer
However, AquaMail uses for the most popular Web mail providers automatically the correct authentication method.