Excel is adding = in front of cells containing @ mark when importing from CSV

Solution 1:

Excel's default and preferred character for starting a formula is =. However Lotus 1–2–3 uses + or - and Apple Works uses @ so Excel also supports them for compatibility

That means if the cell starts with any of the +-=@ characters you'll get a formula. To prevent that from happening prepend ' at the start of the cell. Or force Excel to recognize the formula column as text by selecting Data > Get External Data > From Text, open your CSV file and select the desired type in Text Import Wizard

For more information read

• Excel 2007 is converting CSV fields into formulas
• Bypass excel csv formula conversion on fields starting with + or -