I am currently using my Gmail account (say, email@example.com) to manage several other non-Gmail email accounts (for example's sake, firstname.lastname@example.org and email@example.com). I have emails forwarded automatically from both of those other accounts into my Gmail account. For one of those email addresses (firstname.lastname@example.org), I am also able to send mail through Gmail, and my account is configured to automatically respond to all mail sent to email@example.com with an email from the same address.
Due to institutional policies governing b.com's email account (lack of SMTP access), I can forward mail to Gmail but am unable to send mail as firstname.lastname@example.org from my Gmail account. I would therefore like to reply to all mail sent to email@example.com with an email sent from my account firstname.lastname@example.org. Is there any way to do set that up automatically in Gmail?
Sorry so long.