Exceeding maximum subject length using message.forward

I have searched the site, and the web, but have had no joy.

I have a google apps script attached to a spreadsheet that (among other things) forwards emails with a given label to a given email address. I recently sent an email with a very long subject line, and the script has started failing on the following line of code:

msgsToStore[l].forward(emailAddress);

The error I receive is "Argument too large: subject"

The subject of the original email is 283 characters. Forwarding the message within the gmail web interface works without difficulty, adding "Fwd: " to the beginning as you would expect. The subject contains an ampersand, but is otherwise not unusual.

I need something I can use other than .forward, or some way of modifying the message object before forwarding it, but I can't find any documentation as to what the maximum size is.

Any help is greatly appreciated.

Solution

Trim the subject:

trimmed_subject = msgsToStore[l].getSubject().substring(0, 250)

msgsToStore[l].forward(emailAdress, {
  subject: trimmed_subject, 
});

More details: https://developers.google.com/apps-script/reference/gmail/gmail-message#forward(String,Object)