After some consideration, I chose to go with msmtp. I like its flexible configuration, and it’s just the right size for the job (with room to grow). The major thing I was looking for was STARTTLS support. I wasn’t so concerned with the trust files and certificates, I just had a need to support GMail’s minimum requirements. Yes, msmtp gives you that and the whole 9 yards, for when I need them all.

msmtp Configuration for GMail

With a combination of their official configuration example plus a few targeted suggestions from Grey Bearded Geek’s take at ssmtp, I came up with the following:

# Set default values for all following accounts.
defaults

host  smtp.gmail.com
port  587
timeout  off
protocol  smtp
domain  localhost

# /usr/bin/msmtp --version
#  plain cram-md5 digest-md5 gssapi external login ntlm
auth  on
user  GMAIL-USER
password  GMAIL-PASSWD

tls  on
tls_starttls  on
# WARNING: When the checks are disabled, TLS/SSL sessions will be vulnerable to man-in-the-middle attacks
tls_certcheck  off

logfile  /var/log/msmtp.log
###syslog  on

# A system wide configuration is optional.
# If it exists, it usually defines a default account.
# This allows msmtp to be used like /usr/sbin/sendmail.
account default

# Construct envelope-from addresses of the form "user@oursite.example".
###auto_from on
from  USER@DOMAIN
maildomain  DOMAIN

You plop in the GMAIL-USER and GMAIL-PASSWD, and you’re good to go.

Custom From: Address

I soon learned that the from and maildomain settings are irrelevant; Google will not arbitrarily change the From: header of your mail. That makes sense. So the mail will appear as if it’s coming from you, personally. Well, it turns out that there’s a few things you can do to get around that.

• Create yourself a dedicated GMail account. Now you have isolated your soon-to-be-wildly-popular start-up’s e-mail account from your personal one.
• Follow the instructions on adding a custom From: address to your account. I had to use the older version of the GMail interface to do so. Google will verify that you own the address — you’d better be able to receive mail at that address — and then you can make it your default.

  GMail will now send your mail as it were coming from that address, but it will do so without providing an alias.

• When sending your outbound mail, you can include the following headers:

  From:  ALIAS
  Reply-To:  ALIAS <USER@DOMAIN>

  Google will respect the ALIAS portion of the From: address, though not the address itself. The Reply-To: is optional, but respected in its entirety (alias and address).

Works like a charm.