On 2 PCs I let BOINC projects calculate, which is visible in this picture then for some months due to a problem that was difficult to solve (can't remember precisely what) I stopped with BOINC because I had decided that I'll buy soon a new PC, which I have now (I write this on it). In the mean time, I suppressed the E-Mail address used before for BOINC. Now my new PC is participating in BOINC, visible here with a different mail-address. I changed the E-mail used with BOINC. Now I cannot change the old mail used in BOINC to the new one (message: there is already such a mail address in BOINC). So how can I merge the 2 histories?

BOINC accounts cannot be merged.

But what you can do is change the email address on the old account to rubbish, since BOINC will not check for validity of the email address, so 1234@09876.fpr would be a 'valid' address. After you changed the email address on that account, change the email on the new account to the old email address.

Mind, this will not merge the accounts, because the original account now has a 'new' email address. The email address is the unique identifier.

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