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Should I use a shared IP
Q: address for sending email,
or is a dedicated IP better?
Many ESPs and companies might share
A: a single IP address across multiple senders
or divisions of the company. Because ISPs
monitor mail streams by IP address, sharing IPs
is generally not a good idea if you send large
quantities of email messages.
When you share an IP address with other senders
and they deploy a bad practice — intentionally
or by accident — your messages will be
filtered or blocked by an ISP along with theirs.
Similarly, various block lists may add the shared
IP to their blacklists.
Dedicated IPs cost more than shared IPs, but the
additional costs ensure that you are in control of
your sender reputation and are not affected by a
“bad apple” client of your ESP.
However, you might want to use a shared IP
address if your email volume is extremely low
and/or very sporadic. This is because the ISPs
now factor in the consistency of both volume
and frequency of mailings from an IP. If they see
inconsistency on an IP address, ISPs are likely to
filter mail streams more aggressively.
I just switched IP
Q: addresses. Will this solve
my deliverability problems?
Not by itself. You must be careful when
A: you begin to send email from your new
IP address. Instead of just hitting “send,” you
should build up your reputation gradually on
that IP address.
When the ISPs look at the mail stream coming
from your new IP address, your previous sender
reputation (good or bad) isn’t associated with it. As
a result, most ISPs now prefer that senders “build”
their reputation gradually on a new IP address,
typically over a period of three to four weeks.
While each ISP is different, a general rule of thumb
is to start sending a few thousand messages a
day and then double the amount every four to
seven days. Once the ISP has monitored 50,000 to
100,000 or so emails over the period, you will have
established your initial reputation.
At that point, you should be able to scale up to
higher volumes.
During the ramp-up period, ISPs will be looking at
several factors including:
• Number of concurrent connections
attempted from one mail server
• Number of unknown users (hard bounces)
attempted
• Number of old and inactive (disabled for
12 plus months) accounts being attempted
• Number of spam complaints from recipients
How can the email delivery
Q: reports I receive during and
after email sends help me with
deliverability?
These reports can help you track your
A: delivery rate into the inbox and pinpoint
problems and positive or negative trends. Is your
spam complaint rate rising, perhaps a sign of overmailing?
Did you have a spike in hard bounces — a
result of someone uploading an old list?
Here are some delivery-related processes and
metrics to monitor:
• Hard bounces
• Spam complaints
• Unsubscribes
• Blacklists you have been added to
• Inbox delivery rate by ISP
Where possible, examine these metrics by:
• ISP or domain
• Types of emails including welcome, confirmation,
transactional, announcements/
alerts, newsletters, etc.
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