Dictation of punctuation
When dictating a reply or forward message, you can speak the message and say punctuation to be included.
Speaking Email provides dictation by using the operating system voice recognition APIs. It also depends on the language you are dictating in, which defaults to the language of the email you are replying to, and the locale of your device. For example if the email is English and you are in the US, you should be able to say "period" to get a dot - this is built into the voice recognition system on your device. If you are in the UK you can say "full stop" instead. In non-English languages you can say the appropriate word.
If "period" is not working for you, instead try "full stop". As its more likely you might actually use the word 'period' in a message, we added "full stop" as a synonym that isn't dependent on operating system, language or locale.