Directory Export knows about 2 pseudo fields, 'E-Mail Addresses' and 'Secondary-Proxy-Addresses'. The combination of these two pseudo fields are what you see in the Email Addresses tab of an object.
Both are multi-valued fields, items separated by the separator character you specify in the export.
It isn't possible to only export a certain type of address (such as SMTP), you get the whole field. You can't even be certain which order the addresses will present in if you have different types. What you CAN rely upon is that the 'E-Mail Addresses' field will only have one occurrence of each address type, as by definition you can only have one primary of each address type. (Avoid being confused by the 'E-mail Address' field, which belongs exclusively to a CR and is the real destination address of the object.)
It is perfectly possible to automate the exporting of these fields, a scheduled AT command and an ini file will give you more options than the GUI does. You will need some sort of script to extract the SMTP address, though, if you have multiple address types. This isn't particularly difficult if you know perl, it's a fairly small script. Or you could load the file into Excel and strip the SMPT address out with a formula, or the TextToColumns feature.