[Feature Req] Interface that accept To/CC with a single string

[suntong]

Please consider adding/allowing passing a single string to To/CC. Currently there is an extra check preventing it:

Mail Error: mail: expected single address, got ",a2@gmail.com"; Header: [To] Address: [a1@gmail.com,a2@gmail.com]

Reason being:

• It is perfectly fine to set the "To:" header to something like "Alice <alice@example.com>, Bob <bob@example.com>, Eve <eve@example.com>" in plain email, so such extra checking is too restrictive.
• I understand that there might be extra checking on the email address format checking, but since the basic text based unix email doesn't check it, such extra checking can be optional, IMHO. After all, if the user made mistakes in their to/cc email address, they will know eventually.
• And the most important thing is, to add more recipients, I have to change my code to AddTo to do that, whereas the common sense/practice is to change data, not to change code, when covering different cases.

[xhit]

Hi.

I'm with you.

Currently I'm busy, but If you need this ASAP please send a PR, I will review it.

Thanks.

[suntong]

Currently I'm busy, but If you need this ASAP please send a PR, I will review it.

Closing for the same reason as in #91.