You can setup quotas on each mail DB in Domino, if you click on the Files tab then click on Mail on the left-hand side, right click on the DB that you want then select Quota in the window that opens you can set the quota and the point at which you want them to get a notification that they are getting close to the quota size. We set them at 1- 2 GB when we setup the email account and we increase them as needed depending on the user. CEO mail DB is close to 11GB and we have some shared email addresses that are close to 30GB (customer service).
Lotus Domino Designer 8.5.3
Hope this helps
Lotus Domino 8.5 3 End Of Support
Cross-site scripting (XSS) vulnerability in iNotes 8.5.x in IBM Lotus Domino 8.5 before 8.5.3 FP5 allows remote authenticated users to inject arbitrary web script or HTML via unspecified vectors, aka SPR PTHN95XNR3, a different vulnerability than CVE-2013-0591. 15 CVE-2013-0489: 352: CSRF 2013-03-27: 2017-08-28. 8.5.3 FP2: 13 July 2012 This is mainly a fix release. 8.5.3 FP3: 26 November 2012 This is mainly a fix release. 8.5.3 FP4: 16 April 2013 This is mainly a fix release. 8.5.3 FP5: 8 August 2013 This is mainly a fix release. 8.5.3 FP6: 9 December 2013 Notes/Domino 8.5.3 Fix Pack 6 is the last scheduled Fix Pack for 8.5.3. Lotus Notes/Domino 8.5.3 Fix Pack 4 Release Notice. Notes/Domino 8.5.3 Fix Pack 4 is a scheduled Fix Pack of low-risk, high-impact fixes to help customers safely avoid known issues. IBM strongly recommends that customers running Notes/Domino 8.5.3 upgrade to this latest Fix Pack since it addresses a small percentage of defects.