I'm trying to import quite a big amount of emails (~36 000) and I am always getting this error:
There was a problem with the "title" custom field
We tried to work through it, but your file had too many new values for this custom field and we gave up.
title currently allows the following values: Ms., Mrs, Mr., nd, leaving you with the following options:
* I'll make some changes to my file and re-import it
Remove any of the options for title that aren't listed above and re-import the subscribers again.
* I'll update the options for this custom field so I can re-import my file
This will allow you to add, update or delete your options for title so they match the values in your file.
The problem is title have the correct values (one of the above specified ones). And since it doesn't give any more information about the error, I don't know where to look at...
I tried to reduce the number of emails and then I don't get any errors..
You probably do have some values in your file which are not *exact* matches to the set options for your custom field. After too many of those, the processing stops. Reducing the number of emails just means you encounter less mismatches and they can be automatically handled.
If you contact support and attach the file, we can take a look for you.
Ok, so after more tests it seems that after some unknown values (seems to be around 175) for a specific field, you will get the error. Note that it has nothing to do with the number of different unknown values (that's what I thought at first). So you may have for example 174 times the value 'foo' which is unsupported, it will work and ask you if you want to map these values to a possible one. But if you have one more 'foo', you just get an error.
I think the documentation should be more precise on that. And the error message as well. Like "encountered 175 different values for field 'foo', giving up".