ok, you didn't give a whole heck of a lot of info, but here's a suggestion.
Rather than add a column to a table to store IP counts, use a separate table.
So, your SMTP log could be uploaded into a temp table, the statistics then calculated and stored into a permant SMTPStats table. So, in this example, I have a assumed that your smtp log file has already been uploaded/converted into a table called SMTP_LOG_TEMP, and that the table that contains all your smtp statistics is called SMTP_STATS. SMTP_STATS in this example has 2 fields: IP_ADDRESS, and IP_COUNT.
-- First, get the IPs, and their counts from the latest log file
INSERT INTO #SMTP_STATS_WORK
SELECT IP, Count(IP) as LATEST_COUNT
GROUP BY IP
-- Second, update the SMTP_STATS table
SET a.IP_COUNT = a.IP_COUNT + b.LATEST_COUNT
FROM SMTP_STATS a, #SMTP_STATS_WORK b
WHERE a.IP_ADDRESS = b.IP
-- Lastly, insert any IPs from this run, that weren't in the SMTP_STATS table already
INSERT INTO SMTP_STATS (IP_ADDRESS, IP_COUNT)
SELECT IP, LATEST_COUNT
WHERE IP not in (SELECT IP_ADDRESS FROM SMTP_STATS)