Enclosed documents dont delivers

HI, we have been using CF7 for many years, with the possability to enclose documents, but suddenly a few weeks ago, the enclosed documents dont reach us any more. THe texts work al right but documents no. We have not changed anything for a couple of years, we have the latsest version of CF7.
THe webbhotel LOOPIA advised us to install a SMPT plugin, but that didnt help.
What else can we check for? Is it the lastest version that causing the error?

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