If your email addresses are in separate columns (and you don't want to CC some and BCC others) then you'll want to concatenate your addresses in the 'To' column of your spreadsheet, separated by a comma. Using a simple Excel formula to achieve this probably best.

E.g. Supposing your email addresses are in columns G and H of your worksheet, in the first cell of the column you've set with the 'To' header, you could enter formula =G2&", "&H2 and fill down. This will insert both those recipient addresses into the 'To' field of the draft emails.

UPDATE 14/06/2013: Additionally, you may be experiencing this problem with Notes/Domino treatment of RFC-822 internet addresses with commas. It appears you may be able to work around this issue by enclosing the separate names & addresses in quotes (and/or internet addresses in square-brackets).

As per example above, if you need your addresses surrounded in quotes, try an Excel formula like: =""""&G2&""", """&H2&"""" or if you find it more readable: =CHAR(34)&G2&CHAR(34)&", "&CHAR(34)&H2&CHAR(34).

I have confirmed that comma-separated addresses in SendTo fields are not split by Domino automatically, it is treated as one address. This will require a code change to fix, so I will provide this shortly in a new release.

If your email addresses are in separate columns (and you don't want to CC some and BCC others) then you'll want to concatenate your addresses in the 'To' column of your spreadsheet, separated by a pipe character (|). Using a simple Excel formula to achieve this probably best.

E.g. Supposing your email addresses are in columns G and H of your worksheet, in the first cell of the column you've set with the 'To' header, you could enter formula =G2&" | "&H2 and fill down. This will insert both those recipient addresses into the 'To' field of the draft emails.

MailMerge v1.4 now supports multiple addresses in TO, CC, BCC recipient fields.

Separate your addresses with pipe (|) or new-line (char:10 or Alt+Enter) characters.